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Comparative Evaluation of Greenways and Conventional Bus Lanes - Research Findings

DescriptionThe Scottish Executive commissioned research to evaluate 2 Greenway corridors in Edinburgh as an effective means of Traffic Management.
ISBN0 7480 9370 2
Official Print Publication Date
Website Publication DateMay 19, 2000
Development Department Research Programme Research Findings No. 83Comparative Evaluation of Greenways and Conventional Bus Lanes

Colin Buchanan and Partners

As an element of the City of Edinburgh Council transport strategy, an enhanced bus priority scheme, Greenways, has been implemented. Five arterial routes from the City Centre have been treated with two-way bus priority measures, characterised by their green coloured surface and a combination of traffic management and parking measures, and on-street public transport information. In order to explore the 'added value' of the enhanced features of Greenways and increased levels of service this sought to deliver, when compared with traditional or conventional bus priority, the Scottish Executive commissioned Colin Buchanan and Partners to conduct research during 1999. Two Greenway corridors were studied, A8 Glasgow Road and A900 Leith Walk, as well as a conventional bus priority corridor on A7/A701.

Main Findings

  • The introduction of Greenways on the A8 corridor appears to have improved the reliability of the bus service studied on that corridor.
  • Where retail frontage exists the level of 'insulation' from traffic congestion achieved by priority vehicles is greater on Greenways bus lanes than on conventional bus lanes.
  • There is some evidence that Greenways are causing additional delays to non-priority traffic.
  • Passenger boarding on the A8 corridor has increased since the implementation of Greenways in August 1997.
  • Greenways receive more rigorous enforcement throughout their hours of operation than conventional bus lanes.
  • Greenways are frequently blamed by businesses for a decrease in turnover.
  • Bus drivers are most in favour of Greenways, drivers of Emergency Vehicles have more mixed views.
  • The A8 Greenway appears safer for pedestrians and cyclists than the conventional corridor.
  • From the data available, it is not possible to attribute an increase or decrease in cycle use to Greenways.

Greenways

Greenways were introduced in 1997 as part of Edinburgh City Council's 'Moving Forward' transportation strategy. The Greenways concept involved the phased introduction of 26 kilometres of bus lanes on 5 routes in the city, representing a 3-fold increase on existing provision. Phase 1 comprised the implementation of measures on the A8 and A900 corridors, which are the subject of this study. A further 3 routes were opened in late 1998.

There are 8 distinct facets of Greenways that distinguish them from conventional bus priority:

  • Strict enforcement
  • Traffic calming on side streets
  • Cyclist and pedestrian improvements
  • Priority given to public transport, pedestrians and cyclists
  • Live throughout the working day
  • Red lines which prohibit stopping replace yellow
  • Policing and enforcement by a dedicated warden force
  • Improved standard of shelter with comprehensive bus information and branding.

Greenways studied for this research cost approximately £500,000 per kilometre, in comparison with a per kilometre cost for conventional bus priority of £110,000.

Methodology

The research comprised four elements.

  • The definition of a series of possible effects under which to consider both types of bus priority, and the construction of a comparative framework.
  • Comprehensive data collection covering vehicle performance, behavioural change and activity changes on Greenways.
  • Similar data collection for conventional bus priority lanes.
  • Consideration of the relative effectiveness of each type of bus priority, making recommendations how enhanced priority schemes may be made more effective.

A programme of surveys, to provide a comparative basis of Greenway corridors and conventional bus priority on the A7/A701 ('The Bridges'), was carried out. These surveys can be grouped into three categories:

  • Performance
  • Attitudes
  • Secondary Effects.

Performance

Journey Times

Number plate surveys were undertaken on the A8 and A900 Greenways, and on the conventional bus lane corridor. These provided journey times for both priority and non-priority vehicles. This enabled the extent of benefits/disbenefits experienced by priority vehicles compared to non-priority traffic to be determined.

The analysis indicates that where a bus lane has been implemented (there are locations along Greenways which do not contain bus lanes), bus journey times tend to remain constant when car journey times lengthen due to congestion. Taxi journey time profiles generally mirrored those of buses, a function of taxis being allowed to use bus lanes. This was found to be the case for both Greenways and the conventional bus lanes. Where bus lanes are not in place on Greenways i.e. when the physical layout of an area does not permit them, it was found that buses tended to be subject to the same delay as cars.

In terms of the performance of Greenways relative to conventional lanes, where there are bus lanes in place, and no retail frontage, Greenways and conventional lanes perform equally well. Where bus lanes run along retail frontages, Greenways can be seen to perform better than conventional lanes. On sections where the physical layout does not permit bus lanes, the performance of Greenways is likely to be reduced. These findings suggest that enforcement is an influencing factor in the performance of bus lanes.

Reliability

Data from on bus ticket machines on journey timings for a frequent bus service (12 minutes) was analysed. This service travels the full length of the A8 Greenway and the full length of the conventional bus lane corridor. This provided a sample of approximately 1000 bus journeys for each corridor in each direction. The adherence of a bus to its 'scheduled time' was analysed for both before and after Greenways were implemented, effectively identifying the contribution each type of corridor is making to the reliability of the bus service.

Greenways show clear improvements in adherence to scheduled time during the AM peak inbound and PM peak outbound. The conventional bus lane does not show any obvious improvements in either the pre or post Greenways time periods. This is unsurprising since they were unaffected by the introduction of Greenways, and it supports the hypothesis that the improvements in reliability, shown from this analysis on the A8 corridor, are due to the implementation of Greenways rather than other traffic effects. It does not prove that such improvements could not have been achieved with conventional lanes.

Patronage

Ticket machine data for periods before and after implementation of Greenways, for a relatively high frequency bus service, was utilised to analyse passenger boarding trends. This service travels the full length of A8 Greenway and the conventional corridor.

Overall, passenger boardings have increased by some 2%, reversing early declines in bus patronage in Edinburgh. A detailed analysis of the data reveals substantially greater increases on different parts of the routes and at different time periods. Eastbound patronage on this route between 0601 and 0730, and 1601 and 1800, has increased by 12% and 15% respectively; westbound the corresponding increases are both 7%.

Further examination of this data indicates that the increase in the morning period occurred on the conventional corridor travelling into town, and in the late afternoon, evening period on Greenway travelling out of town.

It was not possible to quantify the effects of service changes, during this period upon patronage levels. However, the significance even of small changes in patronage on these high frequency routes, should not be underestimated when considered as a total number of additional passengers.

Face-to-face interviews were conducted with 600 passengers at bus stops on Greenways. In order to establish an unbiased indication of bus passenger awareness of Greenways, and whether or not they would attribute any opinions/answers to them, the interview was structured so as not to prompt any reference to Greenways.

The results support the evidence from ticket machine data on increasing patronage; 11% of the sample use the bus more, with 7% using the bus less although almost æ of these state reasons unrelated to perception of available mode, i.e. change in personal circumstances or walking for fitness. The data also indicates that only 4% of the sample started to use the bus more within the last 2 years i.e. post Greenways, and only 2% of these passengers did not use the bus at all before. It should be remembered that those no longer using the bus were not interviewed.

Enforcement and Infringement

Greenways and conventional bus lanes in Edinburgh are enforced in quite different ways: Greenways are constantly patrolled between 0730 and 1830 by 35 Traffic Wardens and 5 supervisors on any one day, conventional lanes receive 'visits' commencing after 0800 by Parking Attendants.

A comparison of parking infringement tickets/km of retail issued on each corridor was made revealing that tickets/km of retail frontage are comparable for the 2 Greenways corridors but different for the conventional corridor. The similarity between the 2 Greenways may be a function of the same enforcement regime.

Regular bus users travelling to and from work undertook an infringement survey; both moving and stationary infringements were observed. It was found that the number of moving infringements/trip km recorded was greater on the A8 Greenway. Conversely, the number of parking infringements/trip km recorded was greater on the conventional corridor. It may be the case that moving infringements/trip km observed on the conventional corridor are less due to the higher number of parking infringements/trip km observed, discouraging drivers from entering the bus lanes.

Junction Capacity and Block-Back

Detailed consideration of the junctions on Greenways revealed that most were operating reasonably well. However, there were some where the design was reducing the capacity available for general traffic. One example occurs where the bus lane carries through the junction without any setback, halving the capacity. Similarly, where the bus lane commences immediately downstream of a junction which can result in traffic being unwilling to use the inside lane.

A further mechanism by which Greenways could be worsening congestion on junction approaches occurs as a result of their reducing the queuing space available and thus increasing the frequency with which queues block back to upstream junctions. Occurrences of this were observed during video surveys.

Attitudes

Bus and Emergency Service Vehicle Driver Interviews

Structured face to face interviews (48 in total) with bus, ambulance, fire and police drivers gave an insight as to the opinions and perceptions of regular users for each type of corridor. Bus drivers are most in favour of Greenways. When explaining preferences, bus drivers' responses suggest that they see clear benefits in using Greenways over conventional bus lanes. A mixed response was received from drivers of emergency vehicles, with some preferring Greenways, few preferring the conventional corridor and some stating no preference.

Business and Residential Interviews

Interviews with businesses and residents were undertaken on each corridor. The most frequent reason given by businesses for a decrease in turnover was the introduction of Greenways, with the second most popular being changes in parking. In general, the majority of residents surveyed believe they are worse off because of all bus lanes - Greenways and conventional. The perception by residents that there is less parking appears to be the main reason for this.

Secondary Effects

Analysis of Accident Data

In order to ascertain if Greenways had affected the occurrence of accidents, data for 2 years both before and after their introduction was used. In general, and taking no account of the relative traffic volumes, the A8 Greenway appears safer than the conventional corridor. There is also reduction in the occurrence of pedestrian, cyclist and bus accidents on Greenways.

Traffic Flows

The count data analysed for both Greenways corridors shows that traffic volumes have slightly decreased since their introduction.

Cycle Flows

From the data available, it is not possible to attribute an increase or decrease in cycle use to Greenways.

Property Value Trends

Greenways were thought to have some influence on retail properties on the A8 and Leith Walk corridors, making them less attractive, affecting sales and rentals.

Conclusions

This comparative evaluation of Greenways and conventional bus priority has revealed that Greenway has a definite performance advantage. Journey time, reliability, and enforcement are all markedly enhanced by the use of Greenways treatment.

Enforcement and the reduction in infringement on Greenways, with a comprehensive and well resourced operational regime, are important contributors to their success. However, attitudes towards Greenways by adjacent businesses and residents are less positive, especially with regard to parking provisions. Of note is that all bus lanes, whatever their form, are generally disliked by these groups. Bus drivers exhibit a very positive experience of Greenways with all of the sample stating that Greenways provided the fastest journey.

In terms of secondary effects, including accident rates, traffic flows, cycling and property values, performance of both Greenways and conventional bus lanes appears neutral.

Greenways, as evidenced by this research, have made a positive contribution to the City of Edinburgh Council transport strategy, 'Moving Forward.' However, the research concludes that there is scope to improve the design of some junctions on Greenways, and that conventional bus priority would benefit in operational effectiveness, if enforced to the same extent as Greenways.

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