- Group Name: You know who
- Group participants names: Bernet Samuel, Poitevin Joffrey
- Project Title: The impact of pedestrians at roundabout's entry
Roundabouts are getting more used than ever in traffic's organisation. They have the advantage of making the traffic more fluid and offer choices to vehicles regarding the directions to go. Since they are getting very common, particularly in cities, they are also connected to crosswalks. This creates a situation of conflict between pedestrian and the traffic flow. In particular, we have a trade-off between the safety of pedestrians and traffic. We are interested in the question of optimising the effectiveness of the traffic at a classic roundabout’s entry, varying the crosswalk’s location. More precisely: we are going to study the flow of vehicles entering into the roundabout considering different distances between the yield line and the crosswalk. Our personal experience in Switzerland tells us that there are many roundabouts containing a crosswalk right at the entry, which reduces traffic flow.
A standard single-lane roundabout with four legs (A the entry, B, C and D the exits ) under the left-hand traffic rule is assumed, which includes crosswalk and physical splitter island. We can consider the distance between the crosswalk and the yield line to be a storage space used in order to merge into the roundabout. Thus, for an entry vehicle, the entering procedure is divided into two separate parts due to this storage space, first crossing pedestrian flow and then merging into the circulating flow. From the view point of microscopic approach (we don’t consider the geometrical properties of the roundabout), the roundabout entry capacity is estimated based on the gap acceptance theory: a minor flow (the cars at the roundabout entry) want to cross (the crosswalk) or to merge (the circulating flow in the roundabout) but do not have the priority over the major flow (pedestrian, circulation flow). Subjects in minor flow judge the gaps in major flow to decide crossing or merging into major flow. This gap judging behaviour is the gap acceptance behaviour. During the judging procedure, accepted gap is defined as the gap in major flow which is utilised by subjects in minor flow to cross or merge into major flow while rejected gap is defined as the gap in major flow which is neglected by subjects in minor flow.
The question is: how far away should we set the crosswalk from the yield line not to feel the impact of the pedestrian’s flow onto the traffic ? Is it needed to leave a big gap to have good results or are only a few meters far enough ?
We expect that setting the crosswalk further down the road from the yield line will have a positive impact onto the traffic flow. However, in order to have a positive impact on the pedestrian, we expect that it would be enough to put the crosswalk only a few meters away from the yield line.
Brilon, W., Stuwe, B., & Drews, O. (1993). Sicherheit und Leistungsfaehigkeit von Kreisverkehrsplaetzen (Safety and capacity of roundabouts)
A STUDY ON ESTIMATION METHODOLOGY FOR ROUNDABOUT ENTRY CAPACITY CONSIDERING PEDESTRIAN IMPACTS Kang Wan
Microscopic traffic flow model (With Gaptheory)