Methodology. Figure 1 Case study area

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1 Maximising Efficiency in Domestic Waste Collection through Improved Fleet Management Fraser N McLeod and Tom J Cherrett Transportation Research Group, School of Civil Engineering and the Environment, University of Southampton Abstract This paper presents the results of a study funded by the Department for Transport investigating various strategies for optimising domestic waste collections, including joint working arrangements and alternate weekly collection. This was achieved with the aid of routing and scheduling software (Logix by DPS International). Using domestic collection round data from three waste collection authorities in north Hampshire (Basingstoke and Deane, Hart and Rushmoor), a refuse collection vehicle (RCV) mileage saving of 3% was modelled for joint working, where vehicles continued to operate out of their existing depots. This increased to 5.9% when vehicles were re-allocated to depots optimally. The study suggested that to minimise domestic RCV mileage, vehicle depots should be located at the waste disposal sites. Alternate weekly collection was modelled to reduce both vehicle mileage and time taken by around 15%, when compared with a typical scenario of weekly collection of residual waste and fortnightly collection of recyclable waste. These results were based on the assumption that 20% of the residual waste would be directly diverted into the dry recyclables waste stream. The paper also reports on the benefits that might accrue from optimising routes and round structures, introducing longer shifts, combining collections of residual and recyclable waste, relocating depots and allowing an element of commercial waste collection on domestic rounds. Keywords: household waste, alternate weekly collection, joint working Introduction Household waste collections are expensive to operate and in 2005 it was estimated that the average annual operating cost for a single refuse collection vehicle (RCV), driver and crew was around 115,000 (Jacobs Babtie, 2005). Efficient logistics are important, therefore, not only to reduce operating costs but to reduce vehicle emissions and increase recycling levels. This paper considers the general cost benefits that may accrue from adopting various waste collection strategies: Optimising routes and round structures; Lengthening shifts or adding additional shifts; Combining separate collections of residual and recyclable waste; Joint working between neighbouring waste collection authorities; Relocating vehicle depots, including keeping vehicles at the waste disposal sites; Alternate weekly collection; Allowing some commercial waste collection as part of existing domestic rounds. Of these strategies, joint working and alternate weekly collection are being considered more widely by waste collection authorities (WCAs). The concept of joint working initiatives between neighbouring authorities was promoted by the UK government (Prime Minister s Strategy Unit, 2002) as a mechanism that could provide opportunities to improve services and realise economies of scale. Several studies (Jacobs Babtie, 2005; Mazzotti, 2004; Innovation Forum, 2004) have identified ways in which local authorities could improve the efficiency of their waste collection systems through setting up joint working arrangements. These could include sharing vehicle depots and maintenance facilities, sharing disposal facilities (transfer stations, landfill sites, materials recovery facilities (MRFs) or incinerators) and amalgamating elements of the collection rounds themselves either side of local authority boundaries. This latter aspect was modelled in this study. Alternate weekly collection (AWC), where dry recyclables are collected one week and residual waste the following week, is also becoming increasingly popular with WCAs. By reducing the collection frequency of residual waste householders are forced to think more carefully about recycling. According to the Local Government Association (2007) the average recycling/composting rate for councils using 1

2 AWC is 30% compared with 23% for those councils not using AWC, and the ten councils recording the highest recycling rates across the UK have all adopted AWC. Methodology Detailed data were obtained from three WCAs in north Hampshire (Basingstoke and Deane, Hart and Rushmoor, Figure 1). The data included existing vehicle rounds (households on each round and routes taken) and waste volumes collected (weight of waste collected on each round), and were used as the main inputs to the modelling process, which was undertaken with the aid of a vehicle routing and scheduling software package called LogiX, developed by DPS International. Logix was used to calculate round times and travel distances associated with the existing collection rounds and to generate new, optimal collection rounds for the various new operating scenarios. (All such models aim to produce optimal results but these are not necessarily always found due to the complexity and size of the optimisation task.) The time limitations of the study did not permit all collection rounds to be studied. The majority of the modelling was undertaken using approximately one fifth of the residual waste collection rounds of the three Hampshire WCAs. This equated to 25 vehicle days, or 25 sub-rounds (the term sub-round is used in this paper to avoid confusion with a vehicle round, which normally refers to one vehicle week s work). The rounds closest to the three WCA boundaries were chosen, as these were the most likely to show any benefit from joint working. For anyone considering modelling waste collection rounds, it should be noted that a considerable amount of effort is required in preparing the data supplied by the WCAs into a usable format. In this particular study, the vehicle rounds, supplied as lists of street names visited, had to be translated into ordered lists of postcodes, postcodes being the most suitable location format accepted by LogiX. The waste collection strategies were compared using time and distance costs as performance measures. Financial and environmental costs (e.g. vehicle emissions) may be derived from these but are not included in this paper. Figure 1 Case study area 2

3 Results Optimising routes and round structures The first level of optimisation considered was optimising the routes taken on each of the existing subrounds. On one of the sub-rounds, a saving of more than one hour was modelled, due to the fact that the tipping points on the existing route, (the points on the round where the RCV becomes full and must visit the waste disposal site), were poorly placed, involving lengthy journeys to and from the waste disposal site, whereas the tipping points on the optimised route were much more conveniently located. The typical modelled saving on a sub-round was between minutes. The second level of optimisation considered involved redesigning the round structures (which households were allocated to which round) within each of the three separate authority areas. The results across the three areas were different. For one authority, the existing round structure appeared to be practically optimal already, with Logix unable to make any significant improvements; distance savings of 8% and 14% were modelled for the other two authorities. This largest saving equated to an annual distance reduction of approximately 22,000 km for the whole of the WCA, if similar benefits were realised on all of their residual waste collection rounds. These reported savings were over and above those reported for optimising routes, i.e. the base case here assumed that the existing routes had been optimised. Lengthening shifts or adding additional shifts The predominant operating system in waste collection is job-and-finish where, once the collection crew have finished their predefined collection round on any particular day, they are free to go home. This can mean the RCV is potentially under-utilised. In this study it was investigated whether the RCV could be used for longer periods, either by introducing longer work shifts or adding more shifts. Discussions with the WCAs suggested that longer vehicle working hours may not be desirable. One objection raised was that vehicle maintenance costs would rise substantially as there would not be the same dedicated driver-vehicle relationship if double shifting were implemented. There would also be health and safety implications if crews were required to work longer hours in an already physically demanding job. Nevertheless, the transport impacts of longer or additional shifts was assessed here for a case study area comprising 9 sub-rounds in Rushmoor WCA. Vehicle distance savings of 8.5% and time savings of 1.6% were found when the length of the working day was increased from an average of eight hours to an average of 11½ hours. In addition, the number of sub-rounds required was reduced from nine to six and the number of loads (i.e. trips to the waste disposal site) was reduced from 18 to 16. In another scenario, double shifting was considered, with one crew working in the morning and the other in the afternoon. The scenario modelled here was for each crew to work seven hours, giving a vehicle working day of 14 hours (this scenario would only be feasible where there was sufficient daylight to allow this). The modelled results suggested that vehicle distance and time taken would increase, mainly due to the increased number of trips required to the depot to swap crews. Combining separate collections of residual and recyclable waste Combined collections of residual waste and recyclables, using split-bodied RCVs, were compared with separate collections using standard RCVs. In both cases it was assumed that both waste types were collected weekly. The modelled results indicated that separate collections were considerably less efficient than combined collections in terms of vehicle distance travelled and time taken. Vehicle distance travelled was seen to increase by 48% while the time taken increased by 20%. Although combined collections are more efficient than separate collections, one of the Hampshire WCAs reported that the split-bodied compaction mechanisms were highly prone to breakdown which gave significant operational problems. 3

4 Joint working between neighbouring waste collection authorities Joint working was modelled here by redesigning the collection rounds to allow cross-boundary collections to be made, using a combined vehicle fleet sharing depots. In effect, the three Hampshire authorities were modelled as a single super-authority. In the first scenario considered, the allocation of the vehicles to the depots was fixed as per the existing arrangement. However, LogiX was given a free hand to determine the optimal routes and round structures. Under these conditions the modelled savings were rather modest with a time saving of 0.8% (approximately 3½ minutes per sub-round) and a vehicle mileage saving of 3% (approximately 1.7km per sub-round). The annual distance savings were estimated to be around 2,200km, based on the selected sub-rounds only. In the second scenario considered, the allocation of the vehicles to the depots was not fixed, with LogiX able to decide which depot to use for each round. Under these conditions, the total number of sub-rounds produced (24) was one less than previously, the overall time taken was reduced by 1.4% (approximately 6 minutes per sub-round) with a vehicle mileage saving of 5.9% (approximately 3.3km per sub-round). The annual distance savings for the selected rounds were estimated to be around 4,300km. This result demonstrated the fact that some rounds would be better based out of an alternative depot, and in this example, one of the three depots was not used as the other two depots lay in more optimal locations relative to the collection areas in the sub-rounds. Relocating vehicle depots, including keeping vehicles at the waste disposal sites The three existing depot locations, one for each of the three Hampshire authorities, may not be in optimal locations for the current collection work. Two alternative sets of three depots were suggested by the software tool, Site LogiX: one set selected for the whole region (the three Hampshire authority areas) and one set based on the selected sub-rounds only. Substantial savings were found using the depots that were chosen specifically for the selected sub-rounds. Time taken was reduced by 3.4% (15 minutes per sub-round) and vehicle mileage by 14.3% (8km per sub-round). The annual distance savings were estimated to be around 10,500km. It is recognised, however, that these depot locations would not necessarily be optimal for the other sub-rounds which were not selected for detailed analysis. When depots were chosen based on the whole region, the savings were more modest. Time taken was reduced by 2.1% (9 minutes per subround) and vehicle mileage was reduced by 4.5% (2.5km per sub-round) and the annual distance savings were estimated to be around 3,300km. Another scenario considered was keeping vehicles at the waste disposal sites. Given that RCVs must visit the waste disposal sites to unload at the end of the round this seems a reasonable option, from a logistical viewpoint. With vehicles operating out of the two waste disposal sites (one at Farnborough and one at Chineham (Basingstoke)), the resulting rounds reduced the time taken by 3% (13½ minutes per sub-round) and reduced the vehicle mileage by 13.5% (7.7km per sub-round). The annual distance savings for the selected rounds were estimated to be around 10,000km. Interestingly, when the LogiX model was offered the choice of using any of the three existing vehicle depots or the two waste disposal sites as vehicle depots, the two waste disposal sites were preferred for use on all of the sub-rounds and none of the existing depots were used, suggesting the optimality of the waste disposal sites as depots in terms of reducing RCV mileage. It is recognised, however, that the waste disposal site may not be a suitable location for a vehicle depot given the need for an operators licence and the potential issues related to driver and crew access relative to their homes. Alternate weekly collection Alternate weekly collection (AWC) of residual and recyclable waste was compared here to weekly collection of residual waste and fortnightly collection of recyclable waste, a commonly used collection arrangement. It was assumed here that by introducing AWC, the weight of residual waste would be reduced by 20% (this figure being the minimum anticipated by the three Hampshire authorities). It was also assumed that all of the reduction in residual waste would be diverted into the dry recyclables waste stream. This meant that the existing 20% recycling rate would increase to 36%. In practice, it seems likely that some residual waste would be diverted into some other waste streams such as home 4

5 composting, glass taken to bottle banks or other waste taken to household waste recycling centres, which would mean that the combined total of residual waste and recyclable waste would be reduced by AWC. However, it was decided not to attempt to model this complex behaviour as detailed data were not available. Other key factors modelled here were the collection time per bin and the bin setout rate (the numbers of bins presented for collection each week), which would be expected to change with the introduction of AWC. The results for a case study area comprising 16 residual waste sub-rounds and 13 dry recyclables sub-rounds suggested that by introducing AWC, the vehicle distance travelled would be reduced by 14% (6 km per sub-round) and the time taken by 15% (1 hour per sub-round). The annual distance savings were estimated to be around 7,200km. Allowing some commercial waste collection as part of existing domestic rounds Where commercial premises are located close to residential areas, it makes logistical sense to allow an element of commercial waste to be collected as part of the existing domestic collection rounds. This could be particularly beneficial in terms of reducing private contractor collection vehicle mileage and increasing the amount of paper and cardboard recycled, as many commercial businesses produce large volumes of these materials, and under many private collection arrangements, the potential recyclate is taken to landfill. The impact of introducing a small amount of commercial recyclable waste onto domestic collection rounds was modelled here using a case study area comprising 8 sub-rounds from the Hart and Rushmoor WCAs. Four different proportions of commercial waste were modeled taken from data obtained from New Forest District Council (1.7%, 3.2%, 6.3% and 8% of the total weight of waste collected, which equated to 3.9, 7.4, 14.4 and 18.4 tonnes per fortnight of commercial recyclable waste, respectively.) It was shown that the commercial waste load of 3.9T/fortnight could be readily accommodated on the existing rounds without increasing the number of trips required to the waste disposal site, but there was an added vehicle distance of 46.6km (12%) due to the sub-rounds having to be substantially redesigned to accommodate the commercial waste origin points. The time required to complete the rounds was increased by 5%. When the commercial waste weight was increased to 7.4T/fortnight an additional trip to the waste disposal site was required and both the time and distance required increased by 6%. When the commercial waste weight was increased to 14.4T/fortnight, two additional trips to the waste disposal site were required and the time required increased by 12% while the distance increased by 14%. The number of sub-rounds required to do the work increased from 8 to 9 when 18.4T of commercial waste was modelled and the number of trips to the waste disposal site increased by 4 (from 15 to 19). Both the time and distance required increased by 15%. Revenue may be obtained from charges made to businesses for their waste collection and also from payments made by merchants in paper, plastics, glass or other materials. Annual revenue was estimated to be 436 for every tonne of waste collected on a fortnightly basis under a charging scheme used by a Hampshire WCA. The annual collection costs associated with added vehicle mileage were estimated to be between 600 and 800 per tonne, so the scheme would not appear to be cost-effective. One possible advantage of a local authority providing a commercial waste collection service is that there might be fewer waste collection trips in an area, if the number of private contractors servicing could be reduced, which would have a positive impact on overall vehicle mileage and congestion, particularly in retail areas. Conclusions This study investigated a number of options for waste collection and compared the associated time and distance costs. The impact of optimising collection routes and round structures will clearly depend on how good the existing ones are. Optimising routes saved around minutes per round while optimising round structures provided a further saving in the range of 0% to 14% for the three Hampshire WCAs that were used in the case study. Although using longer shifts (average 11½ hours) was shown to provide some savings, the length of the working day is perhaps not feasible. Double shifting increased time and distance due to the assumed requirement of having to travel to the vehicle depot to swap crews. Combining collection of residual waste and recyclable waste using split-bodied 5

6 RCVs was shown to be highly efficient in terms of time and distance, however, in practice, the reliability of these types of vehicle has been questioned. Joint working between neighbouring WCAs was modelled by redesigning rounds to allow them to straddle existing authority boundaries. With vehicles fixed at their existing depots the modelled savings were relatively small, with a time saving of 0.8% (approximately 3½ minutes per sub-round) and a vehicle mileage saving of 3% (approximately 1.7km per sub-round). With vehicles allowed to be reallocated among the three available depots, time taken was reduced by 1.4% (approximately 6 minutes per sub-round) with a vehicle mileage saving of 5.9% (approximately 3.3km per sub-round) and the number of sub-rounds required was reduced from 25 to 24. Alternative depot locations were also considered. With an optimal arrangement of three depots, according to a site locator tool, the time taken was reduced by 2.1% (9 minutes per sub-round) and vehicle mileage was reduced by 4.5% (2.5km per sub-round). The selected depot locations were optimised according to household locations but did not take into account practical factors such as availability of suitable premises. The site locator tool also did not take into account the locations of the waste disposal sites used, which are important considerations. With this in mind, another scenario considered was keeping vehicles overnight at the two waste disposal sites used. The resulting rounds reduced the time taken by 3% (13½ minutes per sub-round) and reduced the vehicle mileage by 13.5% (7.7km per sub-round). From a theoretical standpoint, keeping vehicles at waste disposal sites optimises the RCV mileage, whenever the RCVs are required to be empty when kept overnight at a depot. However, the costs associated with crew travelling to and from work also need to be considered. The results for alternate weekly collection indicated that vehicle distance travelled would be reduced by 14% (6 km per sub-round) and the time taken by 15% (1 hour per sub-round) over the common system of weekly residual and fortnightly recycling collections. Where commercial premises are located close to residential areas it might be beneficial to collect an element of commercial waste alongside domestic recyclable waste, in terms of increasing the amount of paper and cardboard collected. Clearly this would require additional work effort in redesigning collection rounds. It was shown here that the existing domestic recycling rounds could accommodate small levels of commercial waste collection without adversely affecting the round performance. References Innovation Forum (2004) Joint working in two-tier authorities Report of a symposium held on 8/12/2005. Available at (accessed 5 June 2007). Jacobs Babtie (2005) Project Integra. Maximising Collection Efficiency, DEFRA Waste Implementation Programme Local Authority Support Unit Local Government Association (2007). Recycling rates rocket by 30% when councils switch to alternate weekly collection. Press release dated 25 April 2007, available at: (accessed 5 June 2007). Mazzotti, A (2004) A critical assessment of a routing and scheduling application for optimising domestic waste collections in Hampshire, M.Sc. Dissertation, Transportation Research Group, School of Civil Engineering and the Environment, University of Southampton. Prime Minister s Strategy Unit (2002) Waste not, Want not. A strategy for tackling the waste problem in England. The Strategy Unit, November Available at: (accessed 5 June 2007). 6