Emission based traffic management

Summary

A dynamic speed limit (i.e. responding to weather conditions and traffic volumes) was installed to help to reduce air pollutant emissions. The City of Stuttgart developed and implemented in real life a traffic control model for the inner urban area. The measure improves traffic flow by reducing stop-and-go traffic, with particular focus on public transport, pedestrians and cyclists, avoiding any negative impacts on these transport modes.

Implementing sustainable mobility

In the last couple of years the City of Stuttgart has seen major problems with air quality in the city centre due to its basin-like location and the high number of car trips. The city aims to implement a test site to investigate how much the reduction of stop-and-go traffic would help maintain traffic motion at a steady level while reducing traffic emissions and air pollution.

Specifically, this measure aims to maintain continuous low-level movement of traffic by decreasing stop-and-go incidences. At the same time it will strive to lessen any negative effects on pedestrians, public transportation and bicycle traffic. Equally important, the priority traffic network should be maintained to avoid crowding of surrounding residential areas.

An expert report on the Hohenheimer Strasse test site in Stuttgart has revealed that reducing the braking and acceleration process on an inclined road can also reduce emissions (NOx). This test site also showed no undesired traffic migration into residential areas. Due to this report the municipality expects a reduction in emissions on the test site in the city center, especially during peak hours.

In this context the main objective consists of improving traffic flow by reducing stop-and-go traffic. This will lead to a reduction of traffic-related emissions along the test corridor (expected: -10% for NOx and -15% for PM10) by adapting the speed limit to the actual traffic load. The measure will also provide a micro simulation on the peak hours. This also involves safeguarding the primary road network in order to avoid migration of traffic to residential areas.

Public transport, pedestrians and cyclists are also considered to avoid any negative impacts on these transport modes. Another important objective is to raise public awareness for the measure.

Progress

In 2013 concerned stakeholders chose the final test site and the city council opted to widen the test area to include Cannstatter Strasse. Subsequently the municipal office of public affairs (including the Integrated Traffic Management Center) and the civil engineering office decided where the relevant signage should be established. Upcoming construction sites and the location of the electric cables where taken into consideration. The civil engineering office and the office of public affairs checked the costs and the final location of the signs. To ensure that the road user obeys the speed limit, the City of Stuttgart will has implemented certain traffic laws such as stationary and dynamic speed monitoring.

Measurements of indicators taken before the implementation of the measure, including traffic volumes, travel times, noise and air pollution indicators have all been completed. The municipality implemented the measure Cannstatter Strasse, which is also considered a soft measure. This measure involves constantly changing signposted messages and shows the car driver the 'right' dynamic speed required to get to the next traffic light without any stop. The dynamic speed changes according to traffic-light programming and includes traffic jam recognition. This measure has been implemented. The second pre-measuring after the implementation of the measure Cannstatter Straße and before the implementation of the 2MOVE2 test site, including traffic volumes, travel times, noise and air pollution indicators was done in May 2014. In spring 2015 all the dynamic traffic signs were put up and the software to operate them from the Integrated Traffic Management Center was installed, tested and is now in full operation. On the 1^st of October 2015 the last measuring took place including traffic volumes, travel times, noise and air pollution indicators. In the following months all the measurements will be compared and evaluated.

Outcomes

• The operation of the dynamic speed signs along federal road B14 was successfully launched in April 2015.
• The measure got a wide positive response in the local press.
• The test site is in operation and the dynamic speed signs are one more useful tool for the daily operation of the Integrated Traffic Management Center Stuttgart.