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What Have Been The Effects Of Ruc On Traffic Levels?
Durham implemented a congestion charge for entering and utilising Sadler Street which is the cul-de-sac road that provides access to Durham’s historic cathedral area. Santos (2004) and Wafer (2007) both report that traffic on that road fell by up to 85% from pre charging situations. The Durham case study may be considered the closest example to the textbook model of road user charging since its operation reflected the requirement of levying a charge for traversing a particular stretch of road as advocated by Walters (1964). No other impacts have been reported and there is little further analysis of this scheme in the available literature.
CUPID (2004) reported that the traffic flows in Trondheim dropped between 5-7% when a road pricing package was introduced. However we must bear in mind that the objective of the Norwegian schemes was primarily to raise revenue rather than to control car usage and therefore large reductions in traffic were not sought. This thus underlies the importance of defining carefully the scheme objectives as mentioned in Chapter 2.
Other real world examples of road pricing are more complex as they are expected to have significant traffic impacts on the traffic network. The inter play of network effects is an important consideration in the overall evaluation of the scheme benefits.
We attempt to draw insights from the three following implemented schemes.
• Singapore originally implemented an area licence charge (known as the Area License Scheme (ALS)) to enter the Central Business District in July 1975. Initially vehicles were required to pay a fee to enter this Restricted Zone between the hours of 0730 -0930 (Monday to Friday). In August 1975, this was extended to end at 1015. Since its initial implementation the scheme has undergone a variety of changes and modifications. In this chapter, we look at the immediate short run impacts of the traffic flows on vehicles as it gives an important picture of the possibilities of changes in the traffic flow patterns of employing such a traffic restraint policy using information from Holland and Watson (1978). In 1998, Singapore subsequently revised the technology of the pricing system from a manual license to an all electronic tolling system to charge per entry into the Central Business District as well as other key arterials, with all day time varying charges. This latter scheme is known as the Electronic Road Pricing (ERP) Scheme. The Singapore case study is interesting because we can consider the impacts on traffic flows due to a change in the scheme operation to an electronic tolling system in 1998 which charges for an individual trip as opposed to the previous flat fee per vehicle regardless of number of times of entry. This is the current operating scheme in Singapore and information can be found in Menon (2000).
• London implemented a congestion charge of £5 in February 2003 to enter and drive a vehicle within the area of Central London bounded by the Inner Ring Road. The charge was raised to £8 in July 2005 and the area extended in February 2007 to include the Western Extension. The background of the London Congestion Charging Scheme (LCCS) and details of its operation can be found in Deliverable D3 as well as many published papers in the literature (e.g. Santos, 2004, Santos and Fraser, 2006) and various TfL reports (TfL (2003-2008). TfL (2003) also gives detailed traffic reports and analysis of the pre-implementation situation. It is important to point out that several changes have taken place in London simultaneous with the implementation of the congestion charge. This include the development of a major junction within the charging zone as well as the renewal of the Victorian pipe system, both measures are likely to have serious impacts on travel time and congestion within the charging area. External factors such as the general background traffic decline in London as noted by TfL (2003) can also exaggerate the impact of the congestion charge. In addition, there were other extraneous influences (namely the threat of terrorism and an underground derailment) that occurred during the operation of the scheme.
• The Stockholm trial ran from 3rd January to July 31 2006. During this period charges were levied on vehicles for entering the city of Stockholm and these charges varied by time of day ranging from SEK 10 to SEK 20 (approximately €1.10 to €2.20) with a maximum charge per day of SEK60 (€6.60). (Further details of the scheme and the exemptions may be found in Deliverable D3 as well as Eliasson et al (2009) and Stockholmsförsöket (2006a,b)). While the scheme is now permanent with minor variations to the design, there is limited information available on the current permanent scheme at the time of writing. Just as in London, there was a variety of external factors that makes it difficult to easily separate out the effects of the scheme from other external impacts. For example it is pointed out in Eliasson et al (2009) that there was an accident on an important bridge link which would cloud the picture of the “before scenario”. In addition, about the same time as the trial was in place, there was a fuel price increase in Stockholm which could have had an impact on reducing vehicular traffic.
Bearing the above caveats in mind, we report on the changes in traffic flow, changes in time of day effects as well as changes in delay/speed achieved for each of these pricing schemes examined.
Changes in Traffic Flow
Table 7 1 shows the changes in the number of vehicles entering the Restricted Zone comparing the immediate short run impact of the scheme.
The following facts are evident:
• Cars entering before charging hours commence rose by 24%
• There is a large reduction (over 47%) in number of vehicles entering the zone due to the charge. This masks the actual reduction in cars entering (75%) vis-à-vis pre charge levels (Watson and Holland, 1978)
• When the scheme operated till 0930, there was an increase in the number of vehicles entering the zone after charging hours. This prompted an extension of the operation hours to 1015 which effectively resolved this problem.
Table 7‑1 All Vehicles Entering the Restricted Zone
Source: Watson and
When the initial scheme was implemented, it was enforced by visual inspection. In 1975, labour costs in Singapore were relatively low and this enforcement method was not costly. One of the exemptions was that cars entering the zone carrying four or more passengers were exempted from paying the charge. Table 7 2 shows the number of car pools (defined by the authorities as passenger cars with four or more occupants) entering the Restricted Zone. This exemption led to a surge in the number of car pools entering the zone during the operation hours of the scheme.
Table 7‑2 Carpools Entering the Restricted Zone
Source: Watson and
While it is clear that there is a significant reduction in traffic, detractors in the literature (e.g. Toh,1977; Wilson (1988); McCarthy and Tay (1993)) have all pointed out that the charge might have been set too high and as a result there has been over restraint and therefore an under-utilisation of road space.
When Singapore switched over contiguously to the ERP scheme in 1998, Menon (2000) reported that there was a significant reduction in the number of vehicles entering the charge zone vis-à-vis pre ERP with figures in the range of 15% (for the entire day) and 16% (for the morning peak period). In other words, fine tuning the charges with the ERP system continued to manifest reductions of traffic in a system which originally had a licensing scheme (albeit at a fixed fee) in place.
TRAFFIC ON BYPASS ROUTE
There exists a bypass route around the periphery of the charging zone which carries traffic bound for the charging zone as well as orbital traffic. There is evidence to suggest that the speeds fell with ERP. However the most likely reason for this is that drivers would reroute onto this bypass to avoid having to pay the charge if bypassing the zone. Consequently with increased traffic flows, there is a consequent reduction in travel speeds as shown in Table 7 3.
Table 7‑3 Traffic Circulating on
Source: Menon (2000) Table 1 p. 42
Table 7‑4 Traffic Entering
Source: Table 3.1 p. 41 TfL(2008)
The longer run impacts (comparing 2007 vs 2002) are also important since there may be a time lag for traffic to adjust to the changed conditions produced by charging. While it is clear that the reduction in the number of cars entering the zone has stabilised at around 36%, the initial increase in powered two wheelers reported in 2003 has subsequently been reduced to less than the pre-charging numbers in 2002. However there is a sustained increase in the number of pedal cycles (albeit from a low base) and this trend seems to be increasing. In addition when the fee was raised from £5 to £8 in July 2005, TfL surmises that there was only a relatively “indistinct aggregate traffic volume response” in terms of traffic flows entering in the congestion charging zone (TfL, 2007 p.19).
TRAFFIC ON THE INNER RING ROAD
The inner ring road forms the boundary of the congestion charging zone and as passage through it is not subject to payment of the charge, it serves as the most likely diversionary route for through traffic avoiding the zone. TfL (2004) indicated that in the short run there was a 4% increase in vehicle kms travelled for all vehicles on the inner ring road. However, the longer term picture presented in TfL (2008) suggests instead a decline in traffic on the inner ring road back to pre-charging levels. This remains the situation despite changes to the scheme (including the Western Extension).
TRAFFIC ON RADIALS APPROACHING THE CORDON
It is expected that reductions in traffic entering the charging zone should be reflected also in traffic approaching the radial roads inbound and outbound to the zone. Table 7 5 shows the year on year percentage changes in vehicular traffic (4 wheels or more) inbound and outbound observed on the radials. A key figure was the reduction of 5% in traffic in 2003 which has been followed by a year on year reduction of approximately 1%. If the 2006 data was considered to be an anomaly (TfL 2008 p. 50) and can be disregarded, the traffic data is broadly in line with the general recognised background decline in traffic volumes in London that was occurring before the congestion charge (TfL 2008 p. 50).
Table 7‑5 Traffic Inbound/Outbound on Radial Approaches to Cordon
Source: TfL(various years)
During the Stockholm trial, vehicles entering and exiting the city of Stockholm (by passing one of the 18 control points or gantries) were liable to pay a toll as mentioned previously.
TRAFFIC ENTERING/EXITING THE ZONE
Table 7 6 shows the changes in traffic flows comparing the pre-charging scenario (Spring 2005) vis-à-vis the post-charging scenario (Spring 2006). We distinguish the changes by time period as the toll paid varies by time of day.
Table 7‑6 Changes in Traffic in Congestion Charging Zone Comparing Spring 2006 (post charging) with Spring 2005 (pre charging)
Source: Stockholmsförsöket(2006b), Table 1, p. 13
The recorded 22% reduction during the charge period shown in line 1, column 3 of Table 7 6 pertains to an aggregation of changes in traffic entering/exiting the congestion charging zone over the 18 control points. At the individual level, traffic passing through (in both directions) the congestion charging control points fell by between 9% (4,000 vehicles) and 26% (9,000 vehicles) during this same period. The smallest reduction of 9% was recorded on the control point leading to/from Lindingö island and this is primarily attributable to the exemption for traffic to and from Lindingö which crossed the charging zone within 30 minutes. On the other hand the largest recorded decrease of 26% was attributable to drivers diverted onto a parallel bypass corridor instead of travelling through the charging zone.
Table 7‑7 Changes in Traffic for Radials and Outer Approach Roads Comparing Spring 2006 (post charging) with Spring 2005 (pre charging)
Source: Stockholmsförsöket(2006b), Table 1, p. 13
Since the changes for the outer link roads and the outer city roads are all aggregated changes, they mask the within group variations. It is noted in Stockholmsförsöket (2006b, p. 14) that there are “relatively large variations between different roads”. These roads could potentially be diversionary routes but the evidence suggests that this is not the case and that autonomous traffic increases (background traffic growth) could have easily masked the impact of the congestion charge.
Table 7‑8 Traffic Speeds (km/h) with and without ALS
While improvements in speeds within the restricted zone as well as on the inbound radials due to the restrictions, traffic diversion to the Ring Road led to reductions in speeds there. This evidence underlies the importance of considering wider network impacts of a URUC scheme on periphery and alternative routes.
When the ERP system was introduced, Menon (2000) explained that the ability to vary the charges quarterly was useful because this meant that once the traffic speeds dropped below a certain target level (which was found through empirical speed flow relationships to be in the range of 20 to 30 km/h), a revision in the rates could be triggered and rates adjusted upwards so as to price traffic off the roads and maintain speeds at the target level. Conversely, if traffic speeds rose beyond 30 km/h, the trigger mechanism would be activated to reduce the charges to maintain the optimal speeds.
Table 7 4 and Table 7 5 have shown that traffic flows entering London have been reduced. However, there is less information reported in London on speeds. TfL instead uses a measure of excess time taken to travel 1 kilometre in the period under consideration vis-à-vis travel during free flow conditions as a measure of congestion (TfL 2003). Hence the measure relates to the excess travel time taken due to the impacts of stop-go traffic conditions and stationary traffic but will also include some delays due to traffic signal operations (which might vary from period to period depending on signal timing plans implemented).
CONGESTION IN THE CHARGING ZONE
Table 7 9 shows the average excess delays used to capture the impacts of the charge on travel conditions within the zone.
Table 7‑9 Average Excess Delays (minutes per km) in Charging zone
Source: TfL (2005) Figure 4 p.16
Table 7‑10 Mean Excess Delay (min/km) during Charging Hours
Source: TfL (2008) Table 4.1 p. 57
Table 7‑11 Excess Delays (mins per km) on
Source: TfL(various years)
No information on this theme is currently available from the case studies
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