Unity 3D Traffic Simulation investigating the impacts of safe distance on traffic flow : Investigating how safe distance impacts traffic flow on a one lane highway during three road scenarios

Abstract: With ever expanding transport needs and roads becoming increasingly congested, more people than ever before spend significant parts of their daily life stuck in traffic. One common cause of delays and queue formation is drivers attempting to adjust their speed in relation to the vehicle in front. When doing so they often fail to make a perfect speed adjustment. Either they slow down more than necessary or they keep too high speed, eventually catching up to the vehicle in front and forcing the driver to brake or slow down further. With enough vehicles these effects will compound and reduce the average speeds and overall traffic flow. This report aims to investigate the effect of varying the margin of safety, the distance that vehicles aim to keep between each other. In order to do this the game engine Unity was used to create three different simulations containing a 30km one lane road with a speed limit of 72km/h. The first scenario introduced a complete halt on the road for 10min before traffic was allowed to resume for 3min after which traffic flow was measured. Scenario two then repeated the same parameters as scenario one with the introduction of heavier vehicles represented as trucks and subsequently varied the composition of vehicles. In the third scenario the amount of vehicles on the road was increased to simulate higher congestion and the complete halt was replaced with a section with a reduced speed limit. The scenario then ran for 10min before the average speeds and traffic flow was measured. To vary the margin of safety each scenario then modified the distance thresholds for when the vehicles would start to adapt their speed in order to match the vehicle in front in addition to the distance at which the vehicles would initiate an emergency brake. Our findings indicated a clear relationship between a smaller margin of safety and more cars passing through our system. When faced with a varying vehicle composition we saw an increase in the amount of vehicles braking and accelerating throughout the system. When the vehicle composition of the system varied the optimal safe distance varied in turn. This indicates that the optimal safe distance likely should vary for each vehicle type. For our scenario with a section of reduced speed we found that the margin of safety did not impact the overall traffic flow until the system was heavily congested. When simulating the heavily congested road, reducing the margin of safety leads to a higher average speed and higher traffic flow in our system.