Traffic light regulation for a new public transport network

Summary

Vitoria-Gasteiz’ new mobility system is made up of superblocks that free up public space for pedestrians and cyclists, while public transport and car traffic run along a network of main roads connecting these blocks. As part of this redesign, the city changed the regulation of traffic lights to meet the objectives of that superblock design.

Implementing sustainable mobility

The Sustainable Mobility Plan of Vitoria-Gasteiz established a network of basic roads along which all the motorized ways of transport run, either public (bus, tram and taxis) or private, discouraging the traffic in the rest of the network.

The former traffic light regulation was excessively rigid due to the consecutive incorporation of new regulated intersections. Traffic lights phases were too long and not adapted to the dominant flows changing over the time of the day, producing a limitation of the capacity of the road network.

The purpose of the measure was redesigning the whole city traffic light regulation scheme in order to meet the following objectives: give fluency, through a sequence of green lights (green wave), to vehicles in the basic network surrounding the superblocks and, at the same time, give special priority to public transport. Another parallel objective was to discourage traffic from crossing the superblocks.

Progress

The work started with a diagnosis to better understand the traffic demand and the problems generated by the current traffic lights regulation parameters. Then, a description of the new regulation scheme with the detailed definition of the new structure of the intersections and their coordination was performed. Finally, after a definition of the adaptation of the regulation schemes to mobility changes over the day, the new regulation scheme was implemented on the current traffic light network, tuned and validated to verify its efficiency and compliance with the objectives previously defined.

General regulation proposal and software design
A new simulation software capable to model the new regulation scheme and the traffic lights priority policy was developed to:

• Obtain information to synthesise  the plans.
• Make an iterative process for optimising  the plans.
• Validate the plans.
• Obtain results and check them with real data.
• Check the impact of the new regulation scheme on tram/bus travelling time  and give recommendations.
• Define a model for future evaluations.

Two software models were defined:

• BASE model: referred to May 2008 situation. Used for calibration and validation as well as to establish the starting point used to compare the results between the proposed scheme and the existing situation.
• PROPOSAL model: reports the proposed modifications to the circulation and regulation scheme. direct application.

The new scheme improved quite drastically the existing situation, and in particular:

• Improvements in 62 crosses.
• The TRAM PRIORITY model was applied to all intersections ( with no priority for buses in 17 crosses).
• The BUS PRIORITY model was applied in 17 crosses.

Detailed regulation proposal and its simulation
The city was divided in different sub-areas to define the detailed regulation proposal.

We synthesized, listed and described each of the regulation plans, corresponding to each of the sub areas with their basic parameters and its implementation criteria.

After that, we selected the critical crosses to be analyzed. For each of the critical crosses, improvement proposals, individual impacts evaluation and inversion needs have been scheduled on a chart. Afterwards, collective crosses regulation changes impact were analysed with the AIMSUN software.

Demo primary implementation
The following steps were carried out for the implementation of the selected schemes and criteria.

• Implementation procedures and timetable for the new traffic regulation plans. The plan included a progressive implementation by regulation subareas.
• On street implementation of the new plans, according to the conditions defined in the implementation procedures and timetable.
• Fine tuning, according to observed results from on street implementation, to react in real time to any problem as well as to report the recorded incidents in order to refine the plans, if needed, in the critical points.
• Finally, some routes were proposed to check the performance of the new regulation criteria.

Outcomes

The results of the measure implementation were the following ones:

• New traffic light regulation completed over 230 intersection regulators.
• Reduction of travel time in 7 selected itineraries.
• Reduction of waiting time at crosses, being the stop time reduction about 3% and the number of stops 17%.
• Reduction of not used green traffic light time.