Research Report AP-R Assessment of the Effectiveness of On-road Bicycle Lanes at Roundabouts in Australia and New Zealand

Transcription

1 Research Report AP-R Assessment of the Effectiveness of On-road Bicycle Lanes at Roundabouts in Australia and New Zealand

2 Assessment of the Effectiveness of On-road Bicycle Lanes at Roundabouts in Australia and New Zealand Prepared By Axel Wilke, John Lieswyn and Dr Cameron Munro Project Manager Tony Barton Abstract This report documents the research undertaken for Austroads on bicycle lanes at roundabouts. An extensive literature review informed empirical data gathering. The literature review revealed strong evidence that bicycle lanes on the approach and within roundabouts are associated with negative safety outcomes. Limited and inconclusive research was found on high-speed, multi-lane roundabouts. The dominant cyclist injury crash type involved a motorist entering a roundabout failing to give way to a circulating cyclist. Cyclists could maximise their safety by tracking closer towards the inscribed island. Cyclist lateral tracking was observed at urban roundabouts, which showed that they commonly travelled close to the centre of the traffic lane. Where bicycle lanes were present in the circulating carriageway, they were rarely used by riders. When lane markings were changed at roundabouts to encourage lane sharing, this significantly shifted cyclist positions. It was concluded that the presence of bicycle lanes within the roundabout may serve to discourage lane sharing. Highspeed, multi-lane roundabouts were not studied due to the unacceptable risk the researchers would have been exposed to. Motorist approach speeds across a range of single lane and multi-lane roundabouts were measured and found to be surprisingly similar. Within 20 m of the holding line, horizontal and vertical deflection, or limited visibility to the right could be used to reduce vehicle speeds to an equitable speed of desirably 25 km/h (maximum 30 km/h); this would provide greater time for motorists to scan for conflicting movements (including cyclists) and to reduce the severity of any crash that may occur. This additional time would be likely to reduce the most frequent conflict between motorists and cyclists. A key conclusion from the research is that new or modified roundabouts would ideally either have equitable speeds, or provide for cyclists so that they don t have to enter the circulating carriageway. The tangential roundabout design philosophy of English-speaking countries maximises capacity, whilst the radial design philosophy of continental European countries maximises safety of all users. Other useful geometric elements are vertical deflection, horizontal deflection, and tighter approach radii. Strong evidence was found that lane markings that encourage cyclists to claim the lane (for example sharrows) can be effective and are recommended where speeds are equitable. Cycle lanes on the approach should terminate some distance behind the holding line where speeds are low. Where equitable speeds are achieved, approach lanes should not exceed 3.0 m in width so that drivers do not attempt to enter the roundabout alongside cyclists. Where equitable speeds are unachievable, consideration should be given to physical separation on the approach and departure. The report authors cannot provide conclusive guidance on circulatory cycle lanes due to a lack of data and more research is required. All the evidence is pointing towards speed being the major road safety issue at roundabouts. If the underlying fundamental problem is addressed, then the question that this research is supposed to answer (will bicycle lanes at roundabouts improve safety?) will become secondary. Our research shows conclusively that cyclists maximise their safety when they occupy a lane, and this is most easily achieved when speeds are equitable. Publisher Austroads Ltd. Level 9, 287 Elizabeth Street Sydney NSW 2000 Australia Phone: austroads@austroads.com.au About Austroads Austroads purpose is to: promote improved Australian and New Zealand transport outcomes provide expert technical input to national policy development on road and road transport issues promote improved practice and capability by road agencies. promote consistency in road and road agency operations. Austroads membership comprises: Roads and Maritime Services New South Wales Roads Corporation Victoria Department of Transport and Main Roads Queensland Main Roads Western Australia Department of Planning, Transport and Infrastructure South Australia Department of Infrastructure, Energy and Resources Tasmania Department of Transport Northern Territory Department of Territory and Municipal Services Australian Capital Territory Commonwealth Department of Infrastructure and Regional Development Australian Local Government Association New Zealand Transport Agency. The success of Austroads is derived from the collaboration of member organisations and others in the road industry. It aims to be the Australasian leader in providing high quality information, advice and fostering research in the road transport sector. Keywords Roundabout, radial design, tangential design, bicycle lane, circulatory bicycle lane, advanced bicycle storage box, crash analysis, lateral position, lateral tracking, speed, approach speed, equitable speed, speed profiles, Australian Road Rules, Road User Rule, off-road path ISBN Austroads Project No. NS1722 Austroads Publication No. AP-R Pages 79 Published May 2014 Austroads Ltd 2014 This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without the prior written permission of Austroads. This report has been prepared for Austroads as part of its work to promote improved Australian and New Zealand transport outcomes by providing expert technical input on road and road transport issues. Individual road agencies will determine their response to this report following consideration of their legislative or administrative arrangements, available funding, as well as local circumstances and priorities. Austroads believes this publication to be correct at the time of printing and does not accept responsibility for any consequences arising from the use of information herein. Readers should rely on their own skill and judgement to apply information to particular issues.

3 This is a research report only and not to be used by practitioners for technical guidance. Summary Roundabouts are a relatively safer form of intersection for motorists than signalised intersections, but result in a higher rate of crashes for cyclists. This holds especially true in English-speaking countries, where the design prioritises capacity over safety, and is much more pronounced at larger roundabouts. Multi-lane roundabouts are frequently cited by experienced and inexperienced cyclists alike as a source of significant riding stress and a deterrent to riding; fast motor vehicles and bicycles at roundabouts are not a good mix. In an effort to address this, some road controlling authorities have implemented bicycle lanes up to, through and departing roundabouts. However, there is conflicting evidence about the safety effect of such treatments. The purpose of this study is to obtain objective evidence of the effectiveness of on-road bicycle lanes on and near roundabouts that supports the formation of policy and design advice to be included in the revision of the Austroads guides. A Safe System approach is recommended, based on the components safer roads and safer speeds. Research findings A literature review revealed strong evidence that on-carriageway, painted bicycle lanes on the approach and within roundabouts are associated with negative safety outcomes. Limited and inconclusive research was found on high-speed, multi-lane roundabouts. Most safety analyses found that around four fifths of all cyclist injury crashes in roundabouts involve a motorist entering a roundabout failing to give way to a circulating cyclist, suggesting that in many instances motorists are failing to detect the presence of cyclists, or are incorrectly judging their speed. There is correlation between motorist entry speeds and crash rates (for all users, including cyclists). Evidence is pointing towards the potential usefulness of limiting visibility to the right for motorists approaching a roundabout, in contravention of current design guidance, to achieve lower speeds. Speed management can also be achieved through horizontal and vertical design. Observations of cyclist lateral tracking at eight urban roundabouts found that in many instances, cyclists travel through the apex of the circulating carriageway close to the centre of the traffic lane. Furthermore, where bicycle lanes are present in the circulating carriageway, they are rarely used by riders. Australian Road Rule 247 requires riders to use bicycle lanes and given that this does not match existing user behaviour at roundabouts, consideration should be given whether this rule ought to be reviewed. However, the truncation of an approach bicycle lane from 10 m behind the holding line to 20 m, along with bicycle symbols and markings to encourage lane sharing, 1 was found to significantly shift cyclist positions to the right of the lane. In other words, pavement markings can influence cyclist lateral tracking, and by inference the presence of bicycle lanes within the roundabout may serve to discourage lane sharing (and encourage tracking to the left). High-speed, multi-lane roundabouts were not studied due to the infrequency of cyclists on such roundabouts and the difficulties in identifying suitable comparator sites. Motorist approach speeds across a range of single lane and multi-lane roundabouts were surprisingly similar; and average speeds varied from 32.9 to 37.5 km/h and 19.5 to 31.8 km/h at around 20 m and 5 m behind the holding line, respectively. Average speed variation was correlated with the likelihood of encountering a conflicting motorist movement more so than roundabout geometry and sightlines (although these clearly also play a role). The implication of these findings would appear to be that it is within 20 m of the holding line, horizontal and vertical deflection, or limited visibility to the right could be used to reduce vehicle speeds to an equitable speed of desirably 25 km/h (maximum 30 km/h); this would provide greater time for motorists to scan for conflicting movements (including cyclists) and to reduce the severity of any crash that may occur. This additional time would likely reduce the most frequent conflict between motorists and cyclists described above. 1 Shared lane use in this document refers to situations where cyclists take or claim the lane. As such, it refers to vehicular cycling, and not cars and cyclists travelling next to one another. Austroads 2014 page i

4 Key findings One of the key findings of this research is that there is a fundamental difference to roundabout design philosophy between some continental European and English-speaking countries, and the resulting roundabouts provide very different experiences to their users, including cyclists. If the objective is to make roundabouts more cycle friendly, then it would appear that equitable speeds (refer to Table 1 for speed definitions) should be considered so that cyclists can comfortably claim the lane. Where this speed regime cannot be achieved, cyclists should ideally be provided for so that they don t have to enter the circulating carriageway. Most of the findings result from an extensive literature study, although this aligns well with local research and work undertaken for this project. Table 1: Speed definitions 2 Desirable Maximum Equitable Speed 25 km/h 30 km/h High Speed 40 km/h The researchers suggest that further detailed research should be carried out around the following design features: Geometric features: To encourage equitable speeds between the modes on the roundabout approach and circulating carriageway, consideration should be given to one or more geometric elements such as vertical deflection, horizontal deflection (including semi-mountable aprons), and tighter approach radii. The typical tangential roundabout design philosophy of English-speaking countries maximises capacity, whilst the radial design philosophy of continental European countries maximises safety of all users. The findings of this research support the notion that Australasia should explore the radial design philosophy. Radial design philosophy is a significant departure from the status quo and there are certainly issues to be worked through like truck tracking, and this finding should be seen as a start point for a wider industry discussion. This is an area where much further Australasian research is needed. Visibility management: There is some evidence to suggest that restricting visibility to the approach on the right, in contravention to Austroads design guidance, can have positive safety outcomes. Australasian guidance is at variance with some European (and British) guidance, but it would appear that with reducing visibility, approach speeds also reduce, and the relationship between reduced speeds and reduced crash rates is well proven. Circulating cyclists may benefit from approaching drivers having reduced visibility. The more visibility drivers have, the further they scan in the distance for other cars to give way to, increasing the likelihood of a nearby cyclist being overlooked. The relationship between the issue of reduced visibility and the research question is two-fold, as the measure may directly improve safety for cyclists, whilst at the same time achieving a more equitable speed environment. If equitable speeds are achieved through horizontal or vertical deflection, visibility management may not be required. It is evident that the issue of restricting visibility will require more research. Shared lane markings: If equitable speeds are achieved, then pavement markings should be considered to encourage cyclists to claim the lane and, equally, legitimise such cyclist behaviour among motorists. Shared lane markings and advanced bicycle storage boxes at the holding line may encourage shared lane use and increase driver expectations of cyclist presence. Cycle lanes on the approach should terminate some distance behind the holding line where speeds are low. Where speeds are equitable, approach lanes should not exceed 3.0 m in width, so that drivers do not attempt to enter the roundabout alongside cyclists 3. Conversely, cycle lanes can give a false sense of safety and would work against the idea of sharing the lane. 2 This definition refers to roundabout negotiation or maximum entry design speeds. 3 Refer to Figure 5.1 in Austroads (2009) Austroads 2014 page ii

5 Separated bicycle facilities (paths): Where other constraints preclude design speeds that are low enough to facilitate lane sharing then consideration should first be given to providing direct, attractive off-road alternatives. These alternatives should be designed in such a way as not to present an elevated crash risk at adjoining roundabout arms, either through the use of grade-separated crossings, bent-out crossings and accompanying speed control measures for motorists, such as raised tables or traffic signal control. European practice that provides for pedestrian and cyclist right of way is not used in Australasia, but combining reduced traffic speeds and priority crossings directs the safety onus towards the group where all users are experienced and capable, which is consistent with a safe systems approach. Furthermore, it will still be necessary to consider situations where riders choose to use the roundabout irrespective of the presence of an alternative route. Further research is needed in this area. With current practice, it needs to be stressed that roundabouts are the most challenging form of intersection control for cyclists, and with high operating speeds, none of the available on-street treatments will result in a good cycling environment. Bicycle lanes at lower speed roundabouts: The evidence on the safety disbenefits of riding to the left within a roundabout is strong, and so providing bicycle lanes should be avoided. Rather, the mid-block bicycle lane (if present) should end around 20 m behind the holding line in order to encourage mixing of motorists and cyclists on the roundabout approach. This is despite the anecdotal preference by riders for bicycle lanes within roundabouts, particularly where there are lanes in adjoining mid-block sections of the roadway. Instead of bicycle lanes, designers should consider lane markings that encourage shared lane use as outlined above. Roundabout entries can be narrowed in this case. Bicycle lanes at higher speed roundabouts: Where off-road provision is not viable, or is unlikely to be attractive to some groups of cyclists, then physical separation on the approach and departure should be considered, but conclusive guidance on whether or not to provide circulatory cycle lanes cannot be given. There could be safety benefits or disbenefits from providing a cycle lane within the roundabout, through providing a higher level of separation and increasing conspicuity of the facility through colour, or discouraging cyclists from taking the lane when there is no other traffic and thus becoming more conspicuous themselves, respectively. There remains a paucity of evidence on the safety effects of such measures (either positive or negative) and on the behavioural changes that may, or may not, occur from both cyclists and motorists. Therefore, before and after evaluation is recommended where high-speed roundabouts are modified, using observations of road user behaviour as a proxy for safety outcomes in the short term. In this way, further evidence can be gathered on the appropriateness of treatments, and their detailed design refined accordingly. In the longer term, crash rates should be compared for sites that have been retrofitted with these measures. But even with these measures implemented, the roundabout will still provide a challenging environment, and grade separation remains the preferred treatment where operating speeds are high. Austroads 2014 page iii

6 Contents 1. Introduction Problem Research study purpose Scope Overall study method Literature Review Review aims Context Research review Design guidance Literature summary Crash Analysis Aim Aggregate crash data Fieldwork Method Key variables Measures of effectiveness Data collection methods Site selection Fieldwork Results Lateral tracking Speed measurements Discussion Introduction Bicycle lanes in roundabouts and at other locations Road rules Lateral cyclist tracking Equitable speeds Bicycle storage boxes and bicycle symbols High-speed roundabouts Key Findings And Recommendations Key findings Research recommendations References Appendix A Research Questions Appendix B Speed Profiles Austroads 2014 page iv

7 Figures Figure 1: Overall study method... 2 Figure 2: Radial design (left) and tangential design (right)... 3 Figure 3: Radial roundabout example from NZ... 4 Figure 4: Roundabout types by size and capacity... 4 Figure 5: Typical cyclist provision types at roundabouts... 5 Figure 6: Roundabout cyclist / motorist crash types... 6 Figure 7: Typical arcs of concentration of drivers entering a roundabout... 6 Figure 8: Vehicle path analysis derived conflict points... 7 Figure 9: Cyclist crash rates at large urban German roundabouts... 9 Figure 10: Swiss research findings on pedestrian and cyclist accident proportion, by location Figure 11: Relative injury risk for cyclists of different intersection controls Figure 12: Single-lane roundabout treatment recommended by Cumming Figure 13: Cook Highway roundabout before Figure 14: Cook Highway roundabout after Figure 15: Example of a roundabout with a splitter island protecting the approach cycle lane Figure 16: Austroads visibility figure Figure 17: Equivalent British visibility figure Figure 18: Palomino Dr / Sturges Rd roundabout prior to and after reconstruction Figure 19: Example snapshots from video lateral tracking Figure 20: Lateral tracking histogram for Canning Street roundabout Figure 21: Lateral tracking histogram for Canning Street roundabout at holding line Figure 22: Lateral tracking histogram for Mason Street roundabouts at holding line Figure 23: Lateral tracking histogram for Mason Street roundabouts adjacent to splitter island Figure 24: Lateral tracking histogram for Macrae Road roundabouts Figure 25: Lateral tracking histogram for single lane roundabouts on the Gold Coast Figure 26: Average motor vehicle approach speed profiles by site and arm Figure 27: Observed vehicle speeds at 10 m and 5 m from holding line Figure 28: Pavement treatments to encourage lane sharing Figure 29: Grade separation achieved by a suspended roundabout for cyclists Figure 30: High-speed roundabout with physical separation on approach and departure Figure 31: Seaworld Dr / Waterways Dr north arm (Seaworld Dr) Figure 32: Seaworld Dr / Waterways Dr southeast arm (Macarthur Pde) Figure 33: Seaworld Dr / Waterways Dr west arm (Waterways Dr) Figure 34: Old Burleigh Rd / Queensland Ave north arm (Old Burleigh Rd) Figure 35: Old Burleigh Rd / Queensland Ave west arm (Queensland Ave) Figure 36: Cotlew St / Wardoo St south arm (Cotlew St) Figure 37: Cotlew St / Wardoo St west arm (Wardoo St) Figure 38: Cottesloe Dr / Rio Vista Blvd west arm (Rio Vista Blvd) Figure 39: Cottesloe Dr / Rio Vista Blvd south arm (Cottesloe Dr) Figure 40: Palm Beach Ave / Tahiti Ave south arm (Tahiti Ave) Figure 41: Palm Beach Ave / Tahiti Ave west arm (Palm Beach Ave) Tables Table 1: Speed definitions... ii Table 2: Average number of casualties per roundabout per year Table 3: Detection times (seconds) of motorists to observe cyclists Table 4: Comparison of Austroads and British visibility guidance Table 5: Summary of literature review findings Table 6: Countermeasures and evidence of their effectiveness Table 7: New Zealand wide crash data, disaggregated by junction and intersection control Table 8: Victorian crash data Table 9: Variables which may influence cyclist safety at roundabouts Table 10: Proxy measures considered to be correlated with cyclist injuries Table 11: Data collection methods Table 12: Site description summaries Austroads 2014 page v

8 Table 13: Site description for Canning / Pigdon (Melbourne; site 1) Table 14: Site description Mason Street / Mills Street (Melbourne; site 2) Table 15: Site description for Mason Street / McIntosh Road (Melbourne; site 3) Table 16: Site description for Macrae / Ness / Macleod (Perth; site 4) Table 17: Site description for Macrae / Reynolds (Perth; site 5) Table 18: Site description for Old Burleigh / Queensland (Gold Coast; site 6) Table 19: Site description for Palm Beach / Tahiti (Gold Coast; site 7) Table 20: Site description for Seaworld / Waterways (Gold Coast; site 8) Table 21: Site description for Cottesloe / Rio Vista (Gold Coast; site 9) Table 22: Site description for Cotlew / Wardoo (Gold Coast; site 10) Table 23: Overview of lateral tracking and approach speed survey locations Table 24: Lateral tracking results (straight through cycling movements only) Table 25: Average vehicle speeds approaching roundabouts Table 26: Roundabout categories and maximum entry design speeds as per NCHRP Table 27: Research questions, comments, and methods Austroads 2014 page vi

9 1. Introduction 1.1 Problem In comparison to other forms of intersection control, roundabouts have been shown to have lower crash rates (ITE, 2008, Elvik and Vaa, 2004). However, the risk for cyclists relative to motorists is higher at roundabouts than at other intersection types, and especially so in countries such as the UK, Australia and New Zealand, where the balance is towards capacity with safety as a lesser objective, which is inherent in the design philosophy used in the guidelines (Patterson, 2010) and is explained further in section In an effort to address this, some road controlling authorities in Australia and New Zealand have followed some European and UK examples and implemented bicycle lanes up to, through and departing roundabouts. However, there is conflicting evidence about the safety effect of such treatments. Bicycle lanes at roundabouts can help provide connected facilities which may improve perceived safety, raise awareness of motorists, promote cycling as a legitimate form of transport, and give an opportunity to get past queued traffic, thereby in different ways encouraging more people to cycle more often. Through the safety in numbers effect, this may result in improved safety outcomes for individuals (Jacobsen, 2003) although the causal link has not been definitively established. On the other hand, several authors including Daniels et al (2010) suggest bicycle lanes at roundabouts may decrease actual safety. This may be due to the potential for bicycle lanes to increase motor vehicle speeds by reducing deflection, with a consequent reduction in time for drivers to observe and react to cyclists. Bicycle lanes may also encourage cyclists to adopt lane positioning which increases the probability of conflict with motor vehicles. Given the divergent views about the safety of bicycle lanes at roundabouts, there is a need to develop evidence-based guidance on their application. 1.2 Research study purpose The purpose of this study is to obtain objective evidence of the effectiveness of on-road bicycle lanes on and near roundabouts that supports the formation of policy and design advice to be included in the revision of the Austroads guides. 1.3 Scope This research reviews the literature and crash data to identify pertinent variables to inform the development of an observational study. The focus of the study is on the safety implications of bicycle lanes at single and multi-lane urban roundabouts covering both local and arterial roads. Within this scope, the research study aims to provide advice appropriate to the wide variations in roundabout design and function within the road network. Austroads 2014 page 1

10 1.4 Overall study method The method used for this research consists of five sequential stages, as illustrated in Figure 1: 1. Identify and review the relevant literature, and crash data from a selection of jurisdictions. The objective is to identify the current research consensus and key variables worthy of fieldwork observation. 2. From this list of relevant variables, identify those that can be measured (e.g. speed, lateral cyclist tracking). Select sites based on geometry and traffic conditions and ideally which were treated during the study period. 3. Undertake the fieldwork. 4. Analyse the data to build a picture of the relative importance of each of the variables, and to ascertain the effectiveness of bicycle lanes at various types of roundabouts. 5. Prepare well-considered guidance based on the study findings. Figure 1: Overall study method 1. BACKGROUND Literature review Crash analysis 2. FIELDWORK METHOD Observation variables Site selection 3. FIELDWORK Cyclist lateral tracking Motorist speed profiles 4. ANALYSIS Data analysis Statistical checks 5. INTERPRETATION & REPORTING Evidence-based guidance Austroads 2014 page 2

11 2. Literature review 2.1 Review aims Only limited primary research has been undertaken in Australia and New Zealand with respect to the provision of bicycle lanes at roundabouts. However, a large amount of research has been undertaken overseas (primarily in Europe and North America). This overseas literature needs be considered within context, which may not be transferable to Australasia. Nonetheless, there are likely to be key lessons from this evidence that are transferable with appropriate consideration. 2.2 Context This section describes the problem, as stated in section 2.1, in more detail Geometry Speed reduction is a key to cyclist safety. While continental European practice is focused on safety and hence the typically preferred roundabout design is radial (with lower speeds), in English speaking countries a stronger emphasis is on capacity and hence the typical design is tangential (Figure 2), as outlined by Patterson (2010). Figure 2: Radial design (left) and tangential design (right) 4 A radial design has increased deflection and reduced operating speeds (compared to a tangential design). Radial roundabouts may still have splitter islands between directions of travel on each arm, but these islands have parallel kerbs rather than the triangular shaped splitter islands of a tangential roundabout. An example of a radial roundabout design in New Zealand is shown in Figure 3. 4 Source: Figure 3.1 in Herland and Helmers (2002) Austroads 2014 page 3

12 2.2.2 Superelevation Speed within a roundabout is also moderated by a typical 2% negative superelevation; in other words the crossfall of the circulatory carriageway is such that the road drains toward the outside of the roundabout (ITE, 2008). An exception to this is UK practice, where a 2% positive superelevation encourages faster negotiation speeds. Positive superelevation is also not uncommon in Queensland. Figure 3: Radial roundabout example from NZ Types of roundabouts Brilon (2005) presents a typology of roundabouts based on size (inscribed circle diameter) and capacity (average daily traffic volume) as presented in Figure 4. Compact two-lane roundabouts require large vehicles to straddle two approach lanes. 6 Figure 4: Roundabout types by size and capacity 7 Most research reviewed for this report found that multi-lane and larger roundabouts have a statistically significant higher cyclist crash risk than single lane and smaller roundabouts (for example, Arnold et al., 2010). Multi-lane roundabouts are frequently cited by experienced and inexperienced cyclists alike as a source of significant riding stress. In one study, 93% of respondents indicated that multi-lane roundabouts pose a hazard and/or act as a deterrent to cycling (Campbell et al., 2006). 5 Cook-Church roundabout Palmerston North, New Zealand 6 As with the C-Roundabout (Campbell et al 2006) 7 Source: Figure 2 in Brilon (2005) Austroads 2014 page 4

13 2.2.4 Provisions for cycling in roundabouts Typical provisions for cyclists at roundabouts are illustrated in Figure 5. These provisions include mixed traffic, bicycle lanes adjacent to traffic, cycle paths with priority over traffic, and bicycle paths without priority over traffic. Grade separation (i.e. a path or route provided under or over one or more legs of the roundabout) is another provision type (not shown in the graphic). An additional variation on the mixed traffic option is to add bicycle symbols (advisory lane markings or sharrows ) in the general-purpose lanes on the approach and possibility within the circulating carriageway section to encourage mixing between the modes. Figure 5: Typical cyclist provision types at roundabouts 8 Mixed traffic Cycle lane Path with bicyclist priority (as indicated by continuous red lines) Path without bicyclist priority (as indicated by interrupted red lines) Crash types and conflict points Several studies have identified the most common bicycle versus motor vehicle crash types (Campbell et al., 2006, Cumming, 2011b, Layfield and Maycock, 1986). Figure 6 illustrates these types based on analysis of New Zealand data. 8 Source: Figures 1, 2, and 3 in Daniels et al (2009) Austroads 2014 page 5

14 Figure 6: Roundabout cyclist / motorist crash types 9 The most common crash type in all studies is entering motor vehicle versus circulating cyclist. An analysis of Victorian crash data over the period by Cumming (2010) indicates that this crash type accounts for between 68-88% of all cyclist-motorist crashes depending on the road controlling authority category. It has been posited that the preponderance of this crash type is due to motorists who looked but did not see those cyclists who were not in the field of view (Herslund and Jørgensen, 2003, Franklin, 2007). In Figure 7, a cyclist at position C is adopting vehicular cycling 10 lane positioning and is in the field of view, while a cyclist riding on the periphery of the circulating lane (positions A and B) is not in the field of view. Figure 7: Typical arcs of concentration of drivers entering a roundabout 11 Vehicle path analysis can be used to highlight the difference in the number of conflict points depending on the lane positioning adopted by the cyclist (Figure 8). This figure illustrates the far higher number of conflict points in situations where bicycle lanes are provided within a roundabout or where a cyclist does not adopt a central lane position. 9 Authors reproduction of Figure 3.1 in Campbell et al (2006) 10 Vehicular cycling is the practice of riding bicycles on roads in a manner that is in accordance with the principles for driving in traffic 11 Source: Figure 9.3 in Franklin (2007) Austroads 2014 page 6

15 Figure 8: Vehicle path analysis derived conflict points 12 In addition to motorist failure to see entering, sideswipe, and exiting crash types, the blue squares represent the conflict points which occur due to a cyclist either undertaking a vehicle or squeezed by a passing vehicle. Instead of four conflict points for the vehicular cyclist, there are 16 conflict points for the kerbside/peripheral lane cyclist. The analysis by Cumming suggests peripheral and kerbside lane positioning results in four additional cyclist versus cyclist (where the finer dotted lines intersect) conflicts for a total of 24 conflict points. These are not shown in Figure 8 as they are considered to have a low probability of occurrence. The practicability of maintaining a vehicular cycling lane position (especially where speed differentials are high) is discussed later in this report. Swedish research that checked the crash history of 58 single and 14 multi-lane roundabouts found that, with motor traffic and cycle flow data taken into account, multi-lane roundabouts are 2.6 times more hazardous for cyclists than single lane roundabouts, as quoted in Wilke and Koorey (2001). Crash rates for cyclists are suggested to be 15 (Allot and Lomax Ltd, 1991) to 20 (Wood, 2008) times greater than for cars at roundabouts. However, roundabouts have a unit crash rate for all vehicles that is only about half of that of other intersections, which is a benefit that cyclists don t have a share in; hence the above crash rate analysis is probably too pessimistic. 12 Authors revision of presentation figure in Cumming (2011b) Austroads 2014 page 7

16 2.3 Research review Large urban roundabout research Schnüll et al The Federal Institute for Road Transport (Bundesanstalt für Straßenwesen BASt) is a technical-scientific research institution in Germany s Federal Ministry of Transport, Building and Urban Development. An extensive research project was commissioned on intersection design for cyclists titled Sicherung von Radfahrern an städtischen Knotenpunkten [Safeguarding Bicyclists at Urban Intersections]. The executive summary states (Schnüll et al., 1992): On large roundabouts with an outside diameter of at least 40 m 13 and two lane roundabouts, accidents are more common than with other intersection forms. At roundabouts, cyclists 14 are safer on the circulating lanes than on bicycle lanes or bike paths. Large roundabouts can only be made safe for cyclists through over or underpasses. An extensive literature review informed a detailed analysis of the crash history of 12 large and busy urban roundabouts with 54 approaches (i.e. an average of 4.5 approaches per roundabout, with up to 6 approaches). On 30 approaches cyclists and traffic mixed, 24 approaches had bicycle lanes and 14 approaches had cycle paths (9 bi-directional and 5 uni-directional). The roundabouts had an AADT of between 15,000 and 50,000, and between 1,500 and 11,000 cyclists per day. Over the analysis period, 287 cycle crashes were recorded. The crash frequency 15 and the crash rate 16 for cyclists were determined. Figure 9 shows the crash rates for cyclists for each roundabout in the study based on the type of provision. It can be seen that with increasing traffic volumes, the crash rates for cyclists also increased (this was already known from previous studies). Mixed traffic resulted in lower crash rates than roundabouts with bicycle lanes or cycle paths. Trendlines were shown for mixed traffic (R 2 =0.72; 6 data points) and bicycle lanes (R 2 =0.26, which shows a poor linear relationship for the trendline; 5 data points), but not for cycle paths (R 2 =0.95; 4 data points) due to the low number of data points for the latter case. Three of the roundabouts were changed during the analysis period from mixed traffic to some form of separation. At two roundabouts, bicycle lanes were installed, with a minimum post-treatment period of 27 months (2¼ years, and a total of 38 cycle crashes). At one roundabout, shared paths were installed, with the post-treatment period of 25 months (34 cycle crashes). The before-treatment period ranges from 29 to 53 months and covers a total of 45 cycle crashes. In all cases, the crash frequency more than doubled postimplementation. The authors state that the change in cyclist numbers was not monitored during this period, but that it was clear that cycle traffic had not doubled, which would have been necessary to keep the crash risk at the same level post-implementation. As a result, it was concluded that these treatments had resulted in an increased crash risk to cyclists. 13 Urban single lane roundabouts in Germany would typically have an outside diameter between 25 and 35 m, as shown in Figure 4 14 This should the read as adult cyclists, so that the intentions of the quoted researchers are not misunderstood 15 Cycle crashes per approach per year 16 Cycle crashes 10 6 Daily cyclists 365 year Austroads 2014 page 8

17 Figure 9: Cyclist crash rates at large urban German roundabouts 17 An insurance company determined the before-after crash situation for a large roundabout in Bremen (Bremer Stern; 6 legs; all approaches and departures single lane, with a very wide but unmarked circulating carriageway as is typical for large German roundabouts). After the installation of bicycle lanes, the crash frequency had doubled, whilst the number of cyclists had increased by 60% (Schnüll et al., 1992). This represents an increase in crash frequency of 25% for cyclists 18 (assuming that the increase in cycle activity happened immediately, which in reality would have occurred over a longer time period, hence the 25% increase is a conservative value) Radial single lane research Schoon and van Minnen Schoon and van Minnen (1993) undertook research on 201 recently constructed radial design single lane roundabouts in the Netherlands where the circulating bicycle lane provides cyclists with priority over vehicles entering and exiting the roundabout as per the cycle lane graphic of Figure 5. Their key findings were that: Roundabouts resulted in a casualty reduction of 95% for car occupants and 30% for bicyclists19 Analysis of the average number of bicycle accidents per year per roundabout (no account of cyclist volumes or exposure) found that roundabouts with on-road bicycle lanes had more cyclist casualties than mixed traffic for all traffic volumes. Sites with off-road paths resulted in fewer accidents than mixed traffic for AADT of greater than 12,500; presumably, suitable gaps were becoming increasingly rare, with errors of judgement resulting in an increasing number of crashes. The findings are presented in Table 2. On roundabouts with up to 7,500 veh/day, there is little difference in the number of crashes involving cyclists between those with bicycle lanes and those without bicycle lanes. However, roundabouts with separate paths had fewer accidents than those with or without bicycle lanes within the roundabout On roundabouts with more than 7,500 veh/day, those with a separated path had significantly more crashes than those with or without bicycle lanes within the roundabout A red coloured bicycle lane within the roundabout results in fewer cyclist crashes than a non-coloured bicycle lane Physical separation provides a slight benefit for bicycle lanes within a roundabout 17 Based on figure 5.34 in Schnüll et al (1992); note that the original figure did not show the R 2 values 18 Doubling of cycle crashes and increasing cycle traffic by 60% changes the crash rate equation by the ratio of 2 to 1.6, i.e or a 25% increase. 19 c.f. 6% bicyclist reduction found by Harper and Dunn (2003) Austroads 2014 page 9

18 The safety of multi-lane roundabouts is less than for single lane roundabouts for all road users, but it can be adequate if entry to the roundabout is radial, the speed of entry is minimised and separated paths are provided. Table 2: Average number of casualties per roundabout per year 20 AADT No. of roundabouts Mixed traffic Bicycle lane Separate off-road path <7, (+13%) 7,500-12, (+51%) >12, (+330%) 0.09 (-44%) 0.02 (-94%) 0.35 (+52%) Small roundabouts Haller and Brilon Haller and Lange (2000) reported on German research that included traffic behaviour observations at 16 small roundabouts (26 35 m outside diameter urban / 45 m rural). According to their conflict studies at roundabouts with off-road bicycle paths, obstructions and conflict situations for cyclists accounted for approximated 9% of the encounters 21 with motor vehicles. At roundabouts where cyclists were part of mixed traffic, the occurrence of conflicts was substantially lower at approximately 4% of all encounters. Roundabouts with bicycle lanes were excluded from their research since the negative effects of this form of routing may be regarded as assured. The researchers overall conclusion was that small roundabouts are a safe solution for cycle traffic. 22 Brilon (2005) reported on German roundabout design practice as follows: Bicycle lanes at the periphery of the circulating traffic lanes are no longer allowed since they are very dangerous to cyclists (refer to Brilon, 1997, below) Up to a traffic volume of about 15,000 veh/day, cyclists can be safely accommodated in the circulating lane without any additional measures 23 Above this traffic volume separate cycle paths seem to be useful. These, however, should be set back a distance of around 4 to 5 m from the inscribed circle Two lane exits are banned, and large or multi-lane roundabouts are not recommended. Brilon (1997) undertook before-after analysis of 32 newly constructed single-lane roundabouts which found: After installation of roundabouts, there was a 40% reduction in crash frequency involving all road users However, the number of bicycle crashes went up slightly. This increase took place at roundabouts that had marked bicycle lanes on the outer edge of the circulating roadway (where crash numbers went from one to eight). The number of bicycle crashes was more or less unchanged at locations with mixed traffic as well as at locations with separate bicycle/pedestrian paths. 20 Schoon and van Minnen (1993, p.27); translated from the original Dutch by the authors of this literature review. Percentages are changes relative to mixed traffic. Note that path users have priority when crossing the road, as the research was carried out after a law change required motorists to give way to cyclists. 21 In this context, encounter describes the situation when a cyclist and motorist are present at the same time. 22 Refers exclusively to radial roundabouts 23 In Germany most roundabouts are of the continental radial geometry which limits speed; therefore a higher traffic volume may be acceptable for mixed traffic Austroads 2014 page 10

19 2.3.4 Swiss single lane roundabouts Spacek Spacek (2004) reported on Swiss research into the factors affecting roundabout safety. At the time of writing there were about 2,000 roundabouts in Switzerland with 90% of these being compact single lane designs with inscribed circle diameters between 25 and 40 m. The research considered accident numbers per month (before and after conversion to roundabout control), three classes of traffic volume, and geometric parameters including inscribed circle diameter, presence of a mountable truck apron, circulatory roadway width, and the number of arms. Analysis of accident data for 130 roundabouts revealed that the majority of cyclist injury accidents were occurring within the entry area of the roundabouts (Figure 10). Figure 10: Swiss research findings on pedestrian and cyclist accident proportion, by location 24 From the 130 roundabouts in the list, 32 roundabouts were selected for detailed study. At nine roundabouts, additional fieldwork included measurements of driving behaviour (e.g. lane position) and vehicle speed (at 100 m before the roundabout, approach, entry, circulating, and exit locations). The major overall finding was that increased entry speeds resulted in increased crash rates. Other particular findings were: Radial vs. tangential design. The authors tested the British hypothesis that flat entry angles (e.g. tangential design 25 ) achieve reductions in accident frequency and severity compared with steeper angles, based on the idea that deflection gives better guidance to incoming vehicles and that the angles of intersection of the conflicting streams are smaller. This hypothesis was confirmed only with regard to single-vehicle accidents...steep entry angles [] are significantly better than lower angles in respect to both accident frequency and accident severity...the hypothesis therefore was rejected. Thus, for the design standard, it was recommended that the splitter islands should be designed to achieve high entry angles [] of approximately 70 to 80 to lead vehicle drivers as directly as possible toward the central island. Sight distance. The authors tested the hypothesis that improved visibility across the central island and sight distance to the left (to the right in Australia / New Zealand) achieves reductions in accident frequency. This hypothesis could not be confirmed, but based on the research indications the authors recommend that visibility across the central island in principle be blocked, particularly because there can be little doubt that planting or earth banking in the central island area improves intersection conspicuousness (especially at rural sites). 24 Figure 6 in Spacek (2004); note that the graphics relate to driving on the right hand side 25 The authors describe this as widening of splitter island or funnel shaped splitter island Austroads 2014 page 11

20 Deflection. The authors concluded that insufficiently large central islands result in insufficient deflection and higher negotiation speeds (especially at compact single lane roundabouts). Compared with this design element, the other geometric quantities are of lesser importance or become effective only in combination with other elements Belgian research Daniels et al Daniels et al (2009) undertook regression analysis from a before and after study of injury crashes with bicyclists at 90 newly installed roundabouts in Belgium. They compared the crash frequency to the previous forms of intersection control and researched different roundabout design components. The analysis did not control for exposure (i.e. cyclist volumes were not recorded). They found that roundabouts with bicycle lanes appear to perform significantly worse compared to three other design types (mixed traffic, separate cycle paths, and grade-separated cycle paths). The general layout of the roundabouts studied included mixed traffic (n=9), bicycle lanes adjacent to traffic (n=40), bicycle paths with priority over traffic (n=18), and bicycle paths without priority over traffic (n=20) as shown in the graphics extracted from the reviewed study (Figure 5). In addition to these layouts, the sample included roundabouts with grade separated cycle paths (n=3). The characteristics of the 90 sampled roundabouts included 83 with single lane layouts, 40 in urban areas (50 km/h or less) and 50 in rural areas (70 or 90 km/h). Seven multi-lane roundabouts were studied, and six of these were in the higher speed rural environments. In rural high-speed areas, off-road bicycle paths were the most common form of cyclist provision (60% of the sampled rural roundabouts had bicycle paths). The independent (explanatory) variables used were urban/rural, provision type, whether the roundabout replaced a traffic signal or not, presence of pavement colour, separation element (no separation, bicycle lane line, or physical separation), and priority for bicyclists. The treatment group had 411 reported bicyclist crashes versus a control group with 649 crashes. Key findings of their literature review and study included: Influence of roundabouts on cyclist safety. In contrast to Schoon and van Minnen (who found a 30% reduction in cyclist crashes Section 3.3.2), roundabouts are associated with an increased frequency of cyclist injury crashes (an increase of 27% (p=0.05) in injury crashes, and an increase of 42-44% (p= ), depending on the applied dispersion-value k, for crashes resulting in serious injuries and fatalities) Geometry and speed differentials: larger central islands on roundabouts with radial approaches (>10m radius for single-lane roundabouts) have greater deflection and consequently reduce speed differentials, leading to improved safety performance for cyclists 26 Facility type. Bicycle lanes perform worse compared to the three other design types (mixed traffic, separate cycle paths, and grade-separated cycle paths) (p.148). The authors note that generally little is known concerning the (relative) effects of line markings and physical elements between roadway and bicycle lane (p.146) Looked but failed to see. The authors surmised that looked-but-failed-to see errors may have a strong influence in the safety performance of roundabouts for cyclists. The authors attributed this to the visibility of the cyclist without specifying whether this was their position within the lane or their overall conspicuity. The authors noted that the small crash numbers limited the strength of the conclusions and the exclusion of certain variables (vehicle speed, central island radius, lane widths, and traffic volume) meant that other causal relationships could not be explored. 26 Please note that this comment refers to radial roundabouts. For tangential roundabouts, the larger radius is more likely to lead to higher circulatory speeds and consequently greater speed differentials. Austroads 2014 page 12