Budapest University of Technology and EconomicsFaculty of Civil Engineering - Since 1782

Capacity of all circular intersections depends on a lot of traffic and geometrical parameters. The most important parameters regarding capacity are traffic composition and geometrical parameters like radii and width of the circular roadway, distance and width of the legs, etc. However, all of the above depend on traffic composition including penetration of connected autonomous vehicles (CAVs).

 

CAVs has the advantage to communicate with each other as well as with the roadside infrastructure. Being so, CAVs access the necessary information regarding both momentary decisions on movements in the traffic flow based on the data received from vehicles nearby, and mid-long term decisions on state of certain sections of the route to follow such as environmental conditions like temperature and humidity, sight distances and even pavement surface conditions. Besides, the information acquired can processed immediately, resulting immediate decision on whether changing midterm or momentary dynamic parameters applied as well as the route to follow, or not. In case of emerging penetration of CAVs in everyday traffic, capacity usage of the existing infrastructure and traffic safety can reach levels never seen before. The basic reason behind is that eliminated reaction time appears as capacity increase caused by shorter gaps and eliminated reaction time. Furthermore, the information necessary to make some decisions will not be obtained using optical measures but the intention itself that will be transmitted. For example at the entrance of a roundabout, where the vehicle entering will be in possession of the information regarding if the vehicle approaches on the circular roadway leaves the roundabout at the exit or not. This would mean a decrease in the number of stopping vehicles as well as the number of sudden decelerations at the entrance, causing shorter periods of congestion with shorter queues of vehicles.

 

When working up the topic, the candidate has three main tasks. 

    • First, research must be conducted to find relevant publications regarding differences in parameters used for microsimulation between human drivers and CAVs.

    • Second, an analysis and evaluation must be prepared on how the growing penetration of CAVs in real traffic can modify certain parameters of already known equations.

    • Third, the candidate shall determine the consequences of the above, namely how the capacity and certain traffic phenomena will change suggesting some new or modified traffic and geometrical correlations based on the results of the analysis and evaluation above in cases of different penetrations of CAVs in the road traffic flow for certain types of circular intersections.