The safety effect of exchanging car mobility for bicycle mobility

Transcription

1 The safety effet of exhanging ar mobility for biyle mobility Henk Stipdonk & Martine Reurings R

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3 The safety effet of exhanging ar mobility for biyle mobility Substituting a small number of short ar trips with biyle trips R Henk Stipdonk & Martine Reurings Leidshendam, 2010 SWOV Institute for Road Safety Researh, The Netherlands

4 Report doumentation Number: R Title: The safety effet of exhanging ar mobility for biyle mobility Subtitle: Substituting a small number of short ar trips with biyle trips Author(s): Henk Stipdonk & Martine Reurings Projet leader: Henk Stipdonk Projet number SWOV: Keywords: Biyle; yling; ylist; ar; driver; driving (veh); aident prevention; aident rate; fatality; injury; mobility (pers); Netherlands; SWOV. Contents of the projet: This report desribes the analysis of the effet of exhanging passenger ar mobility for biyle mobility on the number of fatalities and serious road injuries in the Netherlands. A preise alulation of this effet was not possible due to a lak of information, instead the report gives a first and rough approximation of the safety effet. Number of pages: Prie: 8,75 Published by: SWOV, Leidshendam, 2010 This publiation ontains publi information. However, reprodution is only permitted with due aknowledgement. SWOV Institute for Road Safety Researh P.O. Box BB Leidshendam The Netherlands Telephone Telefax info@swov.nl Internet

5 Summary This report desribes the analysis of the effet of exhanging passenger ar mobility for biyle mobility on the number of fatalities and serious road injuries in the Netherlands. A preise alulation of this effet is not possible due to a lak of information, but we were able to give a first and rough approximation of the safety effet. The analysis onsiders a substitution of 10% of ar trips shorter than 7.5 km by biyle trips. The analysis is done eteris paribus, thus, all relevant parameters are assumed to remain equal (exept of ourse mobility). Assuming that the inrease in biyle trips is distributed equally over the network, time of day et., as urrent biyle mobility is, the inrease in the number of fatalities and serious road injuries in rashes involving biyles an be estimated. In the same way, the derease in the number of fatalities and serious road injuries in rashes involving ars is estimated, assuming that the mobility derease has the same safety properties as the remaining ar mobility. Firstly, the amount of mobility exhanged (short trips) is alulated, and then expressed as a perentage-hange in the total mobility (all trips) of ars and biyles. Seondly, the effet of extra biyle mobility on rashes involving biyles is alulated. The same is done for rashes involving ars. These alulations are disaggregated by age and gender of the driver, beause risks strongly orrelate with driver age and gender, both for ar drivers and biyle riders. The results of the proedure desribed above show, by age group, the net gain or loss in road safety, related to the mobility exhange. For eah driver age group, the inrease or derease in the number of fatalities and serious road injuries is alulated. For hospitalized ylists in a single vehile rash we only onsider asualties with an injury severity of at least 2 on the internationally used Maximum Abbreviated Injury Sale. Based on the assumptions given, the alulations suggest an annual inrease of 4 to 8 fatalities and of approximately 500 serious road injuries, when 10% of the short ar trips are exhanged for biyle trips for all ages. Further, the results indiate that the number of fatalities dereases if young ar drivers (<35 years) swith to biyles, but when older ar drivers do the same, this inreases the number of fatalities. The number of serious road injuries inreases for pratially all ages due to the ar-biyle mobility shift. Only for 18- and 19-year-old males, it is benefiial to swith to yling. The overall inrease is a onsequene of the very large number of ylists that are treated in hospital as a onsequene of a single vehile rash with a biyle. SWOV publiation R

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7 Contents 1. Introdution Bakground Aim of this report Other appliations of the method Struture of the report 8 2. Method Priniples of the method The different groups of asualties Detailing the method The hange in ar and biyle mobility The hange in the number of asualties Data Mobility data The number of asualties Results Mobility hange The hange in the number of fatalities and serious road injuries Disussion and onlusion Disussion Road type Biyle friendly infrastruture Biyle trips are shorter than the ar trips they replae Car passengers Time of day Comparison to literature Conlusions 25 Referenes 26 Appendix Casualties in rashes with ars or biyles 27 SWOV publiation R

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9 1. Introdution 1.1. Bakground 1.2. Aim of this report The National Institute for Publi Health and the Environment (RIVM) was ommissioned by the Duth Ministry of Housing, Environmental and Spatial Planning (VROM) to start a projet on 'sustainable traffi'. The aim of this projet is to assess and integrate the potential health aspets of transport interventions for air pollution, noise, physial ativity and road safety, in order to identify measures that will most effetively redue the traffi-related disease burden in the Netherlands (Van Kempen et al., 2010). A first exemplary assessment of a transport intervention was arried out in It estimated the possible health benefits of speed limit redutions at nine highway setions in urban areas (Van Kempen, Knol & Shram-Bijkerk, 2006). The effets of traffi realloation from a densely to a less densely populated area by the introdution of a new highway setion (Shram-Bijkerk et al., 2006) were also evaluated. In both studies it was reommended to evaluate the health benefits of interventions influening biyle use. As an example of suh an intervention, Van Kempen et al. (2010) assessed the possible health benefits of the substitution of short-distane ar trips (shorter than 7.5 km) with short-distane yling trips in the Netherlands. Substituting short-distane ar trips with biyle trips has several advantages in the sphere of health and environment. An inrease in the number of people using a biyle instead of a ar for short trips will lead to an inrease of the overall level of physial ativity, whih is good for publi health, and to a derease of traffi-related noise and air pollution. A hange in modal split might affet road safety, beause the hane of road users getting injured or even being killed in a road rash is not equal for all modes of transport. Therefore, RIVM asked SWOV to estimate the effet of the hange in modal split desribed above. This estimation is the subjet of this report. To emphasize the speial ase of a hange in modal shift, namely the substitution of short-distane ar trips with biyle trips, we will speak about the mobility shift from ar to biyle, of mobility shift or of arbiyle shift. The safety of ylists differs from the safety of ar oupants. Cylists are vulnerable road users, who are easily injured when involved in a rash, espeially when a motorized vehile is also involved. Car oupants are far less vulnerable than ylists. On the other hand, ylists do not endanger other road users as muh as passenger ar drivers do, beause of their muh lower speed and mass. In single vehile rashes, ylists are often injured (annually, 5000 serious road injuries in the Netherlands), but seldom killed (annually,10 in the Netherlands), whereas ar drivers are less often seriously injured (1500 hospitalized a year) but far more often killed than ylists (200 a year). So what would happen if people rode their biyles more often instead of using their ars? SWOV publiation R

10 1.3. Other appliations of the method 1.4. Struture of the report It is not instantly lear how road safety is influened by a mobility shift from ar to biyle, beause it ould have both a positive and negative impat on road safety. When people ride a biyle instead of driving a ar, the risk that they run over and kill someone is minimal. On the other hand, the hane that they get killed in a rash inreases. The aim of this report is to determine the safety effet when a relatively small number (10%) of the short ar trips (< 7.5 km) in the Netherlands in the period is replaed by biyle trips. The effet of this exhange on the expeted number of asualties (killed and hospitalized) is omputed in order to find out whether there is a net gain (less asualties) or loss (more asualties). A preise alulation of the effet of this exhange on the expeted number of asualties is not possible due to a lak of information. However, the subjet is important, as the issue relates to publi health and environmental poliies. Knowledge about the safety effet of more yling instead of ar driving may be used in poliy deisions. Therefore, a first and rough approximation of the safety effet is given in this report. Although the method in this report was developed espeially for answering the question of RIVM, it an be, and has been, applied in other ases. In general, the method an be applied in order to answer all researh questions about the road safety effet of mobility shifts. For example, Shermers & Reurings (2009) estimated the safety effet of Different Payment for Mobility (DPM, road priin. Beause motoryles are exempt from DPM, it is possible that DPM leads to a shift from ar to motoryle. Due to the muh higher rash rate of motoryles, even a small inrease in the total number of motoryle kilometres an result in a large derease of road safety. A similar method as the one given in this report was used to alulate the safety effet of this shift. In Chapter 2, the method is disussed, both globally and in detail. The data used are given in Chapter 3, followed by the results of the appliation of the method on these data in Chapter 4. The report ends with a disussion and onlusions (Chapter 5). 8 SWOV publiation R

11 2. Method 2.1. Priniples of the method Car mobility is assoiated with several different risks, for example the risk of beoming a asualty in a single vehile ar rash, a two-ar rash or a rash between a ar and a biyle. Not only ar drivers run a risk, other road users may also beome ar rash asualties. Biyle mobility is also assoiated with risks, suh as the risk to beome a asualty in a single vehile biyle rash or a rash between a biyle and another party. Assuming that the replaed ar mobility and the added biyle mobility have the same risks as the remaining ar mobility and the biyle mobility before the addition, the hange in the number of asualties due to a ar-biyle shift an be alulated. For example, the hange in the number of asualties in a single vehile ar rash equals the derease in ar mobility, multiplied by the risk to beome a asualty in a single vehile ar rash before the mobility hange. The derease in the number of asualties is determined in the same way for eah type of asualty (e.g., asualties among ylists as a onsequene of a ar rash). The total derease of the number of asualties due to the derease of ar mobility equals the sum of the dereases in the number of asualties for all types of asualties. Subsequently, the total inrease of the number of asualties due to the inrease of biyle mobility is determined analogously. In this way not only ar drivers and ylists themselves are onsidered, but also the other road users, whose risk to beome asualties will hange with the mobility shift. As asualties we will onsider fatalities (i.e., persons who died within 30 days after a road rash as a result of that rash) and those who were hospitalized for at least one night. The method as desribed above means that we ompare the safety of the two senarios: Nothing hanges in the use of passenger ars and biyles. A small number of ar trips is substituted with biyle trips. In other words, we ompare the expeted number of fatalities and serious road injuries in the seond senario to the atual number of fatalities and serious road injuries in the first senario. The differenes are an estimate of the net hange of the modal shift from ars to biyles. In the analyses mobility and safety data are stratified by age and gender of the driver. This is important, beause the probability of beoming involved in a road rash is very inhomogeneously distributed over age and gender of the drivers. Further, the short ar trips that will be substituted in our omputations will not be uniformly distributed over driver ages and gender. So we need to stratify them by age and gender as well. In the approah hosen here, we stratify rash data and mobility data by age and gender wherever possible. Three major problems arise when alulating the effet of a mobility shift from ar to biyle: SWOV publiation R

12 2.2. The different groups of asualties The risk per traffi mode, whih we define as the number of asualties per distane travelled, is not onstant under all irumstanes, but it depends on many fators. For example, ar mobility does not bear a uniform risk for every road, day of week, age of driver, et. The same holds for biyle trips. A given ar trip will hardly be replaed by a biyle trip along exatly the same route. This will result in differenes in trip length and risk. The replaed ar trips will not be evenly distributed over the road network. Aurate data on the properties of the ar trips to be substituted, and of the biyle trips that replae them is laking in the Netherlands. In order to proeed with the researh question, assumptions have to be made to get round this lak of data. The main assumption is that the speifi fration of ar mobility to be substituted with biyle mobility has the same safety properties as the remaining ar mobility. Subsequently, the added biyle mobility is also supposed to have exatly the same properties as the biyle mobility before this addition. "The same properties" means that for eah harateristi (exept age and gender), suh as time of day or road type, the ar mobility dereases by the same fator and biyle mobility inreases by the same fator. For example, every road type loses the same fator of ar mobility and gains the same fator of biyle mobility. Car trips always relate to a driver aged 18 or older. We only replae driver trips and not passenger trips. Although one ar trip an be replaed by multiple biyle trips, the possible ar-biyle shift of ar passengers will be left out of the omputation. This introdues a small error. In rashes with more than two vehiles (whih are rare) the existene of the third party is negleted. As desribed in the previous setion, the basi priniple of the method is that the hange in the number of asualties (fatalities and serious road injuries) is alulated per rash type, subdivided into road user type (ar, biyle or other party). This setion lists the rash and road user types. Only the number of asualties in three types of rashes are influened by a ar-biyle shift. These rash types are: 1. rashes where at least one ar is involved, but no biyles; 2. rashes where at least one biyle is involved, but no ars; 3. rashes where at least one biyle and one ar are involved. Crashes where neither a ar nor a biyle is involved, are assumed to remain as they were: their number is not influened by a hange in ar and biyle mobility. Within these rash groups, we an distinguish the following groups of asualties: 1a asualties among drivers in single vehile ar rashes. 1b asualties among ar drivers, resulting from rashes with other parties than a ar or biyle. 1 asualties among other road users than ar oupants and ylists, resulting from rashes with a ar. 10 SWOV publiation R

13 2.3. Detailing the method The hange in ar and biyle mobility 1d asualties among ar oupants, resulting from two-ar rashes. 2a asualties in single vehile biyle rashes. 2b asualties among ylists, resulting from rashes with other parties than a ar or biyle. 2 asualties among other road users than ar oupants and ylists, resulting from rashes with a biyle. 2d asualties among ylists, resulting from two-biyle rashes. 3a asualties among ylists, resulting from a rash with a ar. 3b asualties among ar oupants, resulting from a rash with a biyle. The number of asualties is presumed to be proportional to ar mobility (Group 1) or biyle mobility (Group 2) or both (Group 3). In 1d (and 2d) the number of asualties is supposed to be proportional to the square of ar or biyle mobility. Let M (a, be the distane travelled by ar drivers of age a and gender g and let M b (a, be the distane travelled by ylists of age a and gender g, both before the ar-biyle shift. The first step in alulating the hange in the number of asualties is to determine the hange in mobility. To do so we first alulate the amount of ar mobility that will be exhanged by biyle mobility, µ(a,. Thus, µ(a, is 10% of the sum of the lengths of all ar trips by drivers of age a and gender g, shorter than 7,5 km. The ar and biyle mobility after the ar-biyle shift, M' (a, and M' b (a,, depend on the original ar and biyle mobility and the exhanged mobility, µ(a,: M = M ' ' b M = M b µ ; + µ. The frational hange in ar and biyle mobility, φ and φ b, is the ratio between the exhanged mobility and the original ar or biyle mobility: φ = µ / M φ = µ / M b b ;. Although the absolute hange µ(a, in mobility is the same for ars and biyles, the relative hanges, φ and φ b, are not neessarily equal. The onsequenes of the ar-biyle shift are alulated as a frational inrease in the number of asualties, proportional to φ and φ b. Beause of this, the value of mobility is no longer relevant, one φ and φ b are known. Note that if only φ (a, and φ b (a, were available (e.g. when we do not want to first distinguish between short and long trips), this makes no differene for the proeeding assessment. SWOV publiation R

14 The hange in the number of asualties Crashes involving ars but no biyles Below, it is shown how the expeted hange in the number of fatalities resulting from the ar-biyle shift is omputed for eah type of asualty. The omputations for the expeted hange in the number of serious road injuries an be arried out analogously, and are therefore not written out expliitly in this report. Group 1a: fatalities among drivers in single vehile ar rashes The ar-biyle shift hanges the number of fatalities in single vehile ar rashes from N s to N' s. Stratifiation by age and gender gives N s (a,, whih denotes the number of drivers of age a and gender g killed in single vehile ar rashes. Let the risk to get killed in a single vehile ar rash as a funtion of age and gender, R s (a,, be defined as: R N / M, s = s where M (a, is, as before, the distane travelled by ar drivers of age a and gender g. Assuming that R s (a, doesn't hange if M (a, hanges, we an ompute N' s (a, resulting from the hange in mobility. Indeed, N ' s = R = R = R = N s s s s M ' ' ( M µ ) M ( 1 φ ). ( 1 φ ) From this, it follows that the inrease (whih is in fat a derease, hene the minus sign) in the number of asualties due to the ar-biyle shift, n s (a,, is given by: n s = N ' s N = φ N s s. Denoting the total inrease in the number of fatalities in single vehile ar rashes for all ages and both genders as n s, we get: n s = φ a, g N s. Group 1b: fatalities among ar drivers, resulting from rashes with other parties than a ar or biyle The number of fatalities in this group is written by N o (a, (where o denotes "other"). Here, a and g denote age and gender of the driver of the involved ar. Beause of the assumption that the mobility of other vehiles than ars and biyles is not hanging, the hange in N o (denoted by n o ) is again proportional to the hange in ar mobility, so, analogously to the omputations for group 1a, we get: n o = φ N o and n o = φ a, g N o. 12 SWOV publiation R

15 Group 1: fatalities among other road users than ar oupants and ylists, resulting from rashes with a ar We denote the number of fatalities in group 1 as where we again stratify by age and gender of the ar driver, who was not killed, so therefore we added a tilde () to the symbol N. We get: N o n o = φ N o and n o = φ a, g N o. Group 1d: fatalities among ar oupants, resulting from two-ar rashes Here we have to stratify by age and gender of two different drivers. One drives ar 1 of whih the driver is killed, the other drives ar 2. After a arbiyle shift, both drivers drive less, by an amount φ (a 1,g 1 ) and φ (a 2,g 2 ) respetively (with a 1 and g 1 the age and gender of the driver of ar 1, and a 2 and g 2 the age and gender of the driver of ar 2 ). This gives a double effet on the expeted new number of fatalities. Both effets are alulated separately. We first alulate the derease in fatalities due to a hange in mobility of possible asualties. Let N (a 1,g 1 ) be the number of fatalities in ars 1 resulting from a rash with another ar ( 2, of whih not neessarily an oupant is killed). The hanges in this number due to the ar-biyle shift is denoted by and omputed as follows: n n = φ ( a, g ) a1, g1 1 1 N ( a1, g1). Next, let N ( a 2, g 2 ) be the number of fatalities in the other ar ( 2 ). So it is the number of fatalities among oupants of ars whih rashed in whih at least one oupant was killed ( 1 ). The effet of the hange in ar mobility in this number is denoted by n and omputed as follows: n = a2, g2 φ ( a2, g 2 ) N ( a2, g 2 ). The total effet is the sum of n and n, equal to n + n ( N N ). = φ + a, g Crashes with biyles but not with ars Note, however, that this is not exatly equal to the derease of the number of fatalities in ar-ar rashes resulting from a hange in ar mobility. Indeed, fatalities in rashes in whih both drivers shift to yling are ounted twie. As long as φ is small, this is a negligible error. The error yields a small overestimation of the assessed derease in the number of ar-ar asualties. The next four groups onern ylists. The omputations are exatly the same as the omputations for ar drivers. Similar notations are used, the SWOV publiation R

16 index is however replaed by b for biyle. For eah group only the resulting hanges in the number of fatalities are given. Group 2a: fatalities in single vehile biyle rashes n bs = a, g φ N b bs. Group 2b: asualties among ylists, resulting from rashes with other parties than a ar or biyle n bo = a, g φ N b bo. Group 2: asualties among other road users than ar oupants and ylists, resulting from rashes with a biyle n ob = a, g φ N b ob. Group 2d: asualties among ylists, resulting from two-biyle rashes n bb + n Crashes with biyles and ars bb ( N bb N bb ). = φb + a, g For asualties in rashes between biyles and ars, the effets of the dereasing ar mobility and the inreasing biyle mobility have to be taken into aount. We still assume φ and φ b to be small, so that we an assume that the effets are linear. We thus assume that the number of ar drivers does not hange when estimating the effet of a ar-biyle shift on the number of asualties among ylists and vie versa. Group 3a: fatalities among ylists, resulting from a rash with a ar The number of ylists killed due to rashes with ars is influened by the mobility of biyles as well as the mobility of ars. The inreasing biyle mobility will lead to an inrease in the number of fatalities, whereas the dereasing ar mobility will lead to a derease in this number. Let N b (a, denote the number of fatalities among ylists of age a and gender g in a rash with a ar and let denote the number of fatalities among N b ylists in a rash with a ar, where the driver of that ar has age a and gender g. Then, analogously to the omputations for rash group 1d (and rash group 2d), the inrease in the total number n b of fatalities among ylists in rashes with ars is omputed as follows: n b = a, g ( φb N b φ N b ). 14 SWOV publiation R

17 Again, a small error ours, as the extra ylists of age a and gender g annot rash with themselves in a ar. Due to this error we perfore slightly underrate the derease in the number of fatalities. Group 3b: fatalities among ar oupants, resulting from a rash with a biyle. This is a very small group beause usually, in a ollision between a biyle and a ar, the ylist is hurt, and the ar oupants are not. Nevertheless we estimate these numbers. In the same way as in Group 3a we find: n b = a, g ( φb N b φ N b ). In this formula, N b (a, denotes the number of fatalities among ar drivers with age a and gender g and N b denotes the number of fatalities among ar drivers who rashed with a ylist of age a and gender g. SWOV publiation R

18 3. Data In this hapter we disuss the data that is used for the atual omputations. Setion 3.1 desribes the mobility data and Setion 3.2 the data about asualties Mobility data The mobility data for the omputations is obtained from the National Travel Survey (OVG, DVS). The OVG uses a sample of households, and eah person within these households is requested to reord all journeys made on a partiular day. Age and gender of the persons are known, where age is binned in age groups. Some other variables reorded are trip length and mode of transport. Road type is not available. To alulate the safety effet of a ar-biyle shift, we analysed data on mobility, in two biennial periods: and The total ar and biyle mobility in these two periods is given in Table 3.1, expressed in distane travelled in billions of kilometres. The table distinguishes short and long trips. Exept for short ar trips, mobility inreased Car km Car >7.5 km 1, , Biyle km Biyle >7.5 km Table 3.1. Distane travelled (in billions of kilometres) by ars and biyles on short and long trips for the periods and For the omputations in this report we need to separate the distane travelled for males and females, as well as for different age groups. This is also available in OVG. Figure 3.1 and Figure 3.2 show the numbers. From Figure 3.1 it follows that males travel a far larger amount of kilometres by ar than females, espeially in long ar trips. Figure 3.2 shows a ompletely different piture. Females travel a far larger amount of kilometres by biyle than males. It follows that most biyle trips are shorter than 7.5 km. 16 SWOV publiation R

19 Distane travelled in billions of km's km >7.5 km km >7.5 km Male Female Figure 3.1. Distane travelled on short and long ar trips in 10 9 km for males and females in different age groups and for the periods and (OVG). Distane travelled in billions of km's km >7.5 km km >7.5 km Male Female Figure 3.2. Distane travelled on short and long biyle trips in 10 9 km for males and females in different age groups and for the periods and (OVG) The number of asualties The number of fatalities and of serious road injuries an be obtained from polie reord data (BRON, DVS). For all rashes, age, gender and traffi mode of the parties involved are registered. Thus, the onflit types are also known. For most of the onflit types, the number of asualties registered in the polie registration are reasonably aurate (registration rate of 93% for fatalities, and 80% or more for the severely injured), exept for hospitalized ylists in rashes in whih no motor vehile is involved. These numbers are SWOV publiation R

20 grossly underestimated by polie registration, possibly beause they are often not reported to the polie in the first plae. Reent researh indiates that only 4% of these asualties are registered by the polie (Reurings & Bos, 2009). Therefore, these numbers are estimated by a different method. Data from the National Medial Registration (LMR, Prismant) is used to estimate the number of hospitalized ylists in rashes in whih no motor vehile is involved. The hospitalized are registered in the LMR by age, gender and several other variables suh as traffi mode and injury severity. The LMR distinguishes between rashes in whih motor vehiles are involved and rashes in whih no motor vehiles are involved. Aording to emergeny room surveys, 70% of the rashes where no motor vehiles are involved are single vehile biyle rashes (Van Kampen, 2007). The remaining part of these are mostly rashes between two biyles. Of the latter group, we do not know the age of the other ylist. We therefore annot treat this group as group 2d (the number of asualties among ylists, resulting from two-biyle rashes). Instead, we treat all hospitalized ylists as if belonging to group 2a (asualties in single vehile biyle rashes). By doing so, we perfore slightly underrate the effet of extra yling beause we ignore the quadrati effet of mobility on the inrease in the number of biyle-biyle rashes. An exploratory analysis showed that about one fourth of the hospitalized ylists registered in the LMR as a asualty of a rash in whih no motor vehiles were involved atually had a rash with a ar (Reurings, Bos & Van Kampen, 2007). Therefore, 75% of the number of LMR registered, hospitalized ylists in rashes in whih no motor vehiles were involved, were used in this analysis. The number of hospitalized ylists in a single vehile rash is very large. In fat it strongly dominates the assessment for hospitalized ylists. To make sure that all those hospitalized are really seriously injured (something we do not know if we use polie registered data (BRON, DVS) only), we only use the number of injured persons with an injury severity of at least 2 on the internationally used injury severity sale (MAIS). For all other serious road injuries in this alulation, we do not make this orretion. This overestimates the number of other serious road injuries, as ompared to ylists, beause, in those ases, also minor injuries (less than 2 on the MAIS) are ounted. On the other hand, these data are not orreted for polie underreporting, as the ylist data are. The hospital data on ylists are more aurate (there is less underreportin than the polie reord data. We assume that the effets of overestimation and underreporting approximately level out. As some of the numbers of asualties are quite small, we used polie reord rash data for the period: For serious road injuries we used data for , as these were the only data available. By doing this, we ignore the fat that the development in time might be different for different groups. Still, as a first estimation of the order of magnitude of the effet, this approximation is a useful indiation. The number of asualties (fatalities and serious road injuries) per group (see Setion 2.2) are given in the appendix. 18 SWOV publiation R

21 4. Results 4.1. Mobility hange The frational derease of ar mobility as a funtion of age and gender is omputed for the situation in whih 10% of the short trips (less than 7.5 km) by ar drivers are substituted with biyle trips, see Figure 4.1. Mobility related to short trips is a small perentage of total mobility (10% - 20%), so that a 10% shift of these short trips from ar to biyle redues ar mobility by just 1 or 2 %. The frational derease in ar mobility beomes stronger with age, both for males and females. The mobility hange for women is larger than for men, indiating that female ar mobility generally onsists of shorter trips than male ar mobility. The frational derease of ar mobility is omputed for two periods, namely 1999 and The mobility exhange frations were almost alike for both periods. Thus, for mobility, averaging over eight years does not have any onsequenes. 3% frational redution of ar mobility 2% 1% 0% Mean male age gender female Figure 4.1. The frational redution of ar mobility by age and gender, if 10% of the short passenger ar trips (shorter than 7,5 km) are substituted with biyle trips. A small redution in ar mobility (between 1% and 2%) results in a large inrease of biyle mobility (about 10%), see Figure 4.2. The relative inrease in biyle mobility is muh larger than the relative derease in ar mobility, sine the total mobility of biyles is roughly one tenth of that of passenger ars. For ylists, the relative inrease is highest for 30- to- 40- year-old men and women, and lower for young drivers and elderly drivers. For young drivers the relative inrease is relatively low, beause they yle a lot. SWOV publiation R

22 frational inrease in biyle mobility. 18% 16% 14% 12% 10% 8% 6% 4% 2% 0% mean male age gender female Figure 4.2. The frational inrease of biyle mobility by age and gender, if 10% of short passenger ar trips (shorter than 7,5 km) are substituted with biyle trips The hange in the number of fatalities and serious road injuries For every group of asualties mentioned in Setion 2.4.3, the hange in the number of fatalities and serious road injuries due to the ar-biyle shift is determined. This is done for the same time period The hange in the number of fatalities and serious road injuries is a fration, or a sum of frations of the urrent number of asualties (whih are given in the appendix) aording to the equations in Setion These frations, derived from the exhange in mobility, are given in Setion 4.1. The results stratified by age are shown in Table 4.1 for male asualties and Table 4.2 for female asualties. For example, the effet of the inrease of biyle mobility on fatalities among male drivers aged is an inrease of 0.4 fatalities, whereas the effet of the derease of ar mobility on the same fatalities is a derease of 2.4 fatalities. Overall, the mobility shift onsidered in this report will lead to a derease of two fatalities among male ar drivers aged In this first approximate assessment, the total gain is negative for fatalities, whih means that there is an inrease. The ar-biyle shift is benefiial for young drivers, and detrimental for elderly drivers. Also, it is more benefiial for males than for females. The turning point lies approximately around the age of 35. For serious road injuries, due to the strong influene of the many hospitalized ylists in non motorized vehile rashes, there is a strong negative overall effet, and only the ar-biyle shift for 18- and 19-year-old males would result in a positive effet. 20 SWOV publiation R

23 Male drivers, fatalities Male drivers, hospitalized Age Effet of φ b Effet of φ Net effet Effet of φ b Effet of φ Net effet Total Table 4.1. The expeted hange in the number of killed and hospitalized male asualties (in eight years) due to an inrease in biyle mobility (φ b ) and derease in ar mobility (φ ). Female drivers, fatalities Female drivers, hospitalized injured Age Effet of φ b Effet of φ Net effet Effet of φ b Effet of φ Net effet sum Table 4.2. The expeted hange in the number of killed and hospitalized female asualties (in eight years) due to an inrease in biyle mobility (φ b ) and derease in ar mobility (φ ). SWOV publiation R

24 5. Disussion and onlusion 5.1. Disussion Road type The presented assessment of the effet of a ar-biyle shift is to be onsidered a first rough estimate. The assumptions on whih the presented alulations are based, may give an inomplete piture of what atually happens in a mobility exhange. Several effets have not been taken into aount. Some of them have already been mentioned in Setion 2.1. Below, it will be indiated what the onsequenes are of ignoring these effets on the estimates. Stratifiation of rashes and mobility by road type has not been applied. It is known that a large part of ar mobility takes plae on motorways, while most of the severe rashes take plae on urban roads and urban streets. It is highly probable that short trips hardly influene motorway mobility, so the redution of the number of fatalities and serious road injuries is expeted to be signifiantly higher. Unfortunately, there are no aurate data available on mobility by road type, age and gender. A simple estimation of the order of magnitude of this effet would be, that the effet on the redution of ar-involving rashes would be doubled, as if φ were doubled. This estimation is based on the assumption that about half of the ar mobility takes plae on motorways, and the simplifiation that the relevant rashes our on non-motorways. This would approximately double the positive effet on ar-involving asualties, and therefore reveal a possibly indifferent effet for fatalities, instead of a negative effet. The negative effet on serious road injuries would possibly still be very large, beause relatively many asualties our in rashes where no motorized traffi is involved (falling off one s bike, biyle-biyle rashes et.). These rashes might, as far as we know, our even on very safe roads. As a first improvement of what would happen if we ould aurately stratify our data by road type, it ould be assumed that motorways are not used for short trips. Combined with gross estimations of the amount of mobility on motorways (42%, see e.g. Shermers & Reurings (2009), p ), an improved alulation is possible. Then, the stratifiation of mobility by age and gender has to be assumed equal for different road types. Based on these assumptions, we alulated the effet of a 10% exhange of short ar trips for biyle trips. To do so, we onsidered rashes on roads with a speed limit of up to 80km/h only. Further, in our alulation, we replaed φ as used in Figure 4.1 by higher values: the original values were divided by 0.58 (=1-0.42). The results are shown in Tables 5.1 and 5.2. As ompared to Tables 4.1 and 4.2 (where short trips were supposed to take plae on all roads proportionally), the net effet of a ar-biyle shift is less negative. The inrease in the number of fatalities has about halved. The inrease in the number of serious road injuries, however, has hardly hanged. This is 22 SWOV publiation R

25 beause this number is dominated by biyle rashes in whih no motorized vehile is involved. Male drivers, fatalities Male drivers, hospitalized Age Effet of φ b Effet of φ Net effet Effet of φ b Effet of φ Net effet Total Table 5.1. The expeted hange in the number of killed and hospitalized male asualties (in eight years) due to an inrease in biyle mobility (φ b ) and derease in ar mobility (φ ), assuming that short ar trips take plae on roads with speed limits of up to 80 km/h only. Female drivers, fatalities Female drivers, hospitalized injured Age Effet of φ b Effet of φ Net effet Effet of φ b Effet of φ Net effet sum Table 5.2. The expeted hange in the number of killed and hospitalized female asualties (in eight years) due to an inrease in biyle mobility (φ b ) and derease in ar mobility (φ ), assuming that short ar trips take plae on roads with speed limits of up to 80 km/h only. SWOV publiation R

26 Biyle friendly infrastruture The assumption that no short ar trips are made on motorways is learly an underestimation of reality. Thus, the alulation as presented above an be seen as an approximation of the lower limit of the effet of the ar-biyle shift. On the other hand, the alulation given in Chapter 4 an be seen as an approximation of the upper limit of the effet. Perhaps a ar-biyle shift is more likely where there is suffiient speifi biyle-friendly infrastruture. In that ase, the shift may lead to both shorter biyle trips and more safe biyle routes. This would lead to a redution of asualties after the shift. The estimates in this report would be different if the risks for ylists were dereased by making the infrastruture safer for them. This an be done by reduing speeds on intersetions and by biyle failities along roads Biyle trips are shorter than the ar trips they replae Car passengers Time of day A Duth study (AVV, 2005), aimed at a similar estimation of the effet of a ar-biyle shift, suggests that biyle trips are generally 20% shorter than the ar trips they replae. In this report this possibility was not researhed, but the assumption may be valid, in whih ase the net result of the mobility exhange would be 20% more positive. When some short ar trips with a driver and a passenger are replaed by two or more biyle trips, this would have different safety effets. The passenger, who does not have to be of the same age and gender as the driver, bears a different risk. Suh a alulation is therefore muh more ompliated than a alulation involving drivers only. It an be arried out with the data available, if it an be assumed that a driver and passenger ar trip are replaed by two biyle trips. However, it is not lear that this assumption will influene the result in a negative way. A trip with two ar oupants might either lead to two biyle trips, or to one biyle trip. For an aurate alulation, we are required to know the reason of the ar trips with passengers, and what would atually happen when these trips are exhanged for biyle trips. The subjet of this report originated from environmental issues (Setion 1.1). The subjet is also interesting, however, from another point of view: more yling instead of driving will probably derease traffi jams in rush hours. The effet on road safety of more yling in rush hours an also be omputed. This ould be done analogously to the omputations in this report, needing not only stratifiation by age and gender, but also by time of day. Again, both the mobility effet and the effet on the number of asualties are expeted to depend on time of day. As both rash and mobility data are available, for age groups, gender and time of day, the omputations are possible. 24 SWOV publiation R

27 Comparison to literature 5.2. Conlusions In 2005 the Transport Researh Centre (AVV, now Centre for Transport and Navigation) onduted researh to answer a similar question (AVV, 2005; van Boggelen & Everaars, 2006). Their onlusion is that a shift from ar to biyle mobility will not lead to an inrease in road asualties, whih is a different result than the result in this report. They used a slightly different approah to alulate the safety effet of this modal shift, whih might lead to slightly different outomes. The differene of their onlusion an, however, not be entirely explained by the differene of approah. A more likely explanation for their unhanging number of road asualties is the number of serious road injuries used in their omputations. AVV (2005) only inluded serious road injuries registered by the polie. In Setion 3.2 we explained that this is reasonable for asualties in rashes involving motor vehiles, but that hardly any serious road injuries in other rashes are registered by the polie. So the risk of ylists getting injured in a road rash used in the AVV report is far too low. It turned out to be possible to give a first approximation of the effet on road safety of a mobility shift from ar to biyle. This approximation indiates that, in general, road safety does not benefit from this mobility shift. When 10% of the short ar trips are exhanged for biyle trips for all ages, our alulations suggest an annual inrease of 4 to 8 fatalities and of approximately 500 serious road injuries. The effet of the mobility shift is different for gender and age groups. For example, the researh shows that, after a ar-biyle shift, the number of fatalities dereases for young ar drivers (<35 years) but inreases for older ar drivers. So, espeially elderly drivers are safer inside a ar than on a biyle. For the number of serious road injuries, the mobility shift inreases the number of asualties for pratially all ages. Only for 18- and 19- yearold males, it seems benefiial to swith to yling. Even if the numbers mentioned above are an overestimation by a fator 2, the annual inrease in the number of hospitalized injured patients would still be 250, although in this alulation only 10% of the short trips, whih is just 1% of ar mobility, was exhanged. SWOV publiation R

28 Referenes AVV (2005). Effet toename fietsaandeel op de verkeersveiligheid; Eindrapport. Diretoraat-Generaal Rijkswaterstaat, Adviesdienst Verkeer en Vervoer AVV, Rotterdam. Boggelen, O. van & Everaars, J. (2006). Fietsgebruik stimuleren: de gevolgen voor de verkeersveiligheid. In: Fietsverkeer, mei 2006, p Kampen, L.T.B. van (2007). Gewonde fietsers in het ziekenhuis; Een analyse van ongevallen- en letselgegevens. R Stihting Wetenshappelijk Onderzoek Verkeersveiligheid SWOV, Leidshendam. Kempen, E. van, Knol, A. & Shram-Bijkerk, D. (2006). Transport-related health impat assessment; A first estimation of the health benefits of speed limit redution at 9 highway setions in the Netherlands. Report no 00120/2006 MGO/EvK. National Institute for Publi Health and the Environment RIVM, Bilthoven. Kempen, E. van, et al. (2010). Exhanging ar trips by yling in the Netherlands. Report no /2008. National Institute for Publi Health and the Environment RIVM, Bilthoven. (to appear) Reurings, M.C.B. & Bos, N.M. (2009). Ernstig gewonde verkeersslahtoffers in Nederland in ; Het werkelijke aantal in ziekenhuizen opgenomen verkeersslahtoffers met een MAIS van ten minste 2. R Stihting Wetenshappelijk Onderzoek Verkeersveiligheid SWOV, Leidshendam. Reurings, M.C.B., Bos, N.M. & Kampen, L.T.B. van (2007). Berekening van het werkelijk aantal in ziekenhuizen opgenomen verkeersgewonden, ; Methode en resultaten van koppeling en ophoging van bestanden. R Stihting Wetenshappelijk Onderzoek Verkeersveiligheid SWOV, Leidshendam. Shermers, G. & Reurings, M.C.B. (2009). Verkeersveiligheidseffeten van de invoering van Anders Betalen voor Mobiliteit. R Stihting Wetenshappelijk Onderzoek Verkeersveiligheid SWOV, Leidshendam. Shram-Bijkerk, D., et al. (2009). Quantitative health impat assessment of transport poliies; Two simulations related to speed limit redution and traffi re-alloation in the Netherlands. In: Oupational and Environmental Mediine, vol. 66, pp SWOV publiation R

29 Appendix Casualties in rashes with ars or biyles 1a 1b 1 1d 2a 2b 2 2d 3a 3b age N s N o Ñ o N Ñ N bs N bo Ñ ob N bb Ñ bb N b Ñ b N b Ñ b Table A.1 Data on male driver or ylists, fatalities in 8 years, orresponding to the groups mentioned in Setion 2.3.2, and stratified by age. 1a 1b 1 1d 2a 2b 2 2d 3a 3b age N s N o Ñ o N Ñ N bs N bo Ñ ob N bb Ñ bb N b Ñ b N b Ñ b Table A.2. Data on female drivers or ylists, fatalities in 8 years, orresponding to the groups mentioned in Setion 2.3.2, and stratified by age. SWOV publiation R