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Evidence of the effects of 30 kph limit on traffic flow on major roads and on LSA control

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Geo-spatial type
Project website
STRIA Roadmaps
Network and traffic management systems (NTM)
Transport mode
Road icon
Transport sectors
Passenger transport,
Freight transport


Background & Policy context

In the current guidelines for traffic light systems (RiLSA, editions 2010 and 2015), a maximum speed of 50 km/h is used as a rule for determining entry, clearance and intermediate times and further time calculations. While speeds above this value can be mapped, speeds below 50km/h are only taken into account in few places. Therefore, the necessary changes should be identified and the effects on traffic flow and air pollutant emissions should be investigated.


In recent years, speed limits of 30 km/h have been increasingly imposed on main roads in various major cities.  Therefore, this research project analyses the effect of the speed limit of 30 km/h on traffic flow and air pollutant emissions addressing the question of the choose of the driving dynamics model for the calculation of intermediate times since RiLSA in the version of 2010 and 2015 do not know a speed below 50 km/h. Moreover, the project aims at identifying conflicts and synergies with the management of cycling on the road, especially in the context of "priority times" for cycle traffic next to the roadway and with regard to advanced parking areas. Moreover, it is important to differentiate whether changes in the quality of traffic are driven by lower speeds on the track or in the intersections. In addition, the project tries to answer the question which traffic flow can be expected with comparable traffic demand. Moreover, the research team pays attention to the effect of the speed limit on regulations in terms of air pollutant emissions.


The methodology can be described as follows:
First of all, survey among municipalities and traffic signal system operators on the special features of the control system, the junction geometries, the calculation of intermediate times, the existing traffic loads and the resulting traffic quality (free traffic flow, slow, stop and go traffic) especially on traffic signal systems in lines with a speed of 30 km/ h is conducted.
Second, an evaluation of the survey results and comparison with the specifics of the traffic speeds customary to date (v = 50 km/h or 60 km/h) will take place.
Third, vehicle dynamics considerations are taken into account in order to calculate the intermediate times for the different hostilities (distance/time calculations) and to prove performance (risk of backlog, vehicle throughput, stop and go)
Then, an empirical investigation of intermediate times, broaching speeds and time requirement will be done.
Moreover, the impact on the efficiency of hubs (capacity, travel time difference, congestion, stops) with comparable traffic demand will be determined.
In addition, qualitative assessment of changes in air pollutant emissions will be considered.
Finally, questions will be answered and recommendations for practice will be derived.


Parent Programmes
Institution Type
Public institution
Institution Name
Bundesministerium für Verkehr und dititale Infrastrukturen BMVI
Type of funding
Public (national/regional/local)
Funding Source
Federal Ministry of Transport and Digital Infrastructure


Lead Organisation
EU Contribution
Partner Organisations
EU Contribution


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