Dynamic Speed Limits to improve local air quality Henk Stoelhorst Rijkswaterstaat, Centre for Transport and Navigation

1 Agenda:  Reduction of speed limits due to air pollution  Experience pilot scheme A13 Overschie  Experience on other 80 km zones  Dynamic speed limits  Conclusions

2 Strategic view Dutch Motorway Speed Limits Road design motorway network: 120 km/h (120 where possible) Safety and environmental considerations: 100 km/h near urban areas and ring roads around cities (100 where necessary) Recently, on particular spots with local air quality problems: 80 km/h (80 by exemption)

3 Pilot scheme 80 km/h on Motorway A13 Air quality and noise benefits Reduction NO x - emission traffic: minus 15-25% - background: minus 5-10% Accidents: minus 50% Throughput increases in direction of Rotterdam (queue moves upstream) People living near the motorway and politicians are happy Speed limit observance OK thanks to electronic link enforcement

4 Hot spots local air quality 2002: 80 km/h on pilot scheme A 13 Rotterdam 2005: 4 new 80 km zones

5 Invoering 80 per 1 november

6 Practical experience 80 km zones (1) Local air quality: improved on all spots. Traffic emissions reduce with 20-30% for NOx and 10% PM 10 Noise: measured reduction dB(A), reduction of noise peaks with met 1,0 – 2,5 dB(A) Traffic safety: too limited time period for accident analysis, positive expectation based on structural effect A13 and on speed reductions Throughput: different observations, some sections revealed capacity reductions with congestion increase

7 Practical experience 80 km zones (2) Drivers: experience a higher work load, reduce speed and experience that changing lanes is more difficult. A speed limit of 80 combined with strict speed control will harm traffic efficiency on complex weaving sections with heavy traffic. On a few zones with complex exchange of traffic the 80 km/h with section control gives a reduction of traffic capacity due to a change in driving behaviour Speed flow diagram

8 Safety considerations LocationReduction of speed Reduction of accidents (km/h) (% expected) A10 West A12 Utrecht A12 Voorburg A20 Rotterdam Experience: A13 Overschie shows measured reduction of 50% less accidents. Suppose 5% congestion due to accidents: 2,5 % less congestion!!!

9 Dynamic speed limits Variable speed limits: dependent on time of day, traffic, location, circumstances and weather Current experience with variable speed limits: - road works: 90/70 - motorway traffic signalling (MTM): 70/50 - tests: reduction of speed limit near bottleneck locations to increase throughput - winter and fog conditions: 70/50 via MTM - local air quality: 80 km zones - extra rush hour lanes: lower speed limit

10 Benefits of dynamic speed limits Adjustable to unexpected and changing situations like weather, traffic volumes, accidents and fitted to circumstances Possiblity for road authorities to act immediately, without time demanding procedures or placing road signs Only when needed: no unnecessary delays for drivers More understandable by road user: better acceptance of speed limits

11 Dynamic speed limits programme Masterplan for variable speed limits encompasses behavioural research and 4 areas for experiments: - safety and bad weather conditions - local air quality - throughput/reliability traffic flow - reduction travel time (100 > 120 km/h) Experiments planned for 2008/2009 Legislation to enable experiments

12 Do drivers understand dynamic speed limits?

13 Conclusions Speed limit reductions with strict enforcement are an effective tool to reduce local traffic emissions Be careful when applying the measure on sections with heavy bottlenecks and complex weaving sections Dynamic speed limits dependent on actual circumstances like traffic, weather, road and environmental conditions look promising