In-Vehicle Traffic Light
Effect of In-Vehicle Traffic Light on Driving Behaviour
Motivation:
Emerging vehicular communication makes it possible to transfer information between vehicles and static traffic lights. Therefore, an in-vehicle traffic light system was proposed to assist drivers at intersections with signals and ones without signals by providing virtual traffic light information inside the vehicle with an advance information display. Experiments were performed to analyse the influence of the proposed system on driver behaviour.
Project description:
For the application of in-vehicle traffic lights at signal-controlled intersections, the design of the system was mainly based on vehicle-to-infrastructure communication. Two modes, a “current mode” and a “predictive mode,” of in-vehicle traffic lights were proposed. For the current mode, when vehicles are within the range of the in-vehicle traffic lights, the real-time information of the static traffic lights at the intersection ahead will be displayed directly to drivers on in-vehicle devices.
The predictive mode will provide advance static traffic light information for the intersection ahead based on the current driving speed of the vehicle and the distance to the intersection. This mode considers the status of the static traffic lights that control the lane the vehicle is in and the vehicle’s anticipated time to the intersection. The design of the system was mainly based on vehicle-to-vehicle communication for an in-vehicle traffic light system at non-signal-controlled intersections.
There are two types of non-signal-controlled intersections: two-way and multiple-way stop-controlled intersections. At a two-way stop-controlled intersection, the roads that are not controlled by stop signs are defined as major roads. Conversely, stop-controlled roads are referred to as minor roads. Vehicles on major roads have priority to proceed through the intersection first. Therefore, vehicles on major roads will see a green signal on the device after entering the range of the in-vehicle traffic lights. Vehicles on minor roads which are within the range but have not yet arrived at the intersection will be presented with a red light.
The gap on the major road will then be calculated for vehicles on minor roads when they reach the intersection. If this major-road gap is less than 6.5 seconds, a green light will be displayed to vehicles on the major roads, and a red light will be presented to the minor-road vehicle. If a gap greater or equal to 6.5 seconds appears, the red light displayed to the vehicle on the minor road will turn green, and the green light presented to the vehicle on the major road will become a blinking yellow light.
At a multi-way stop-controlled intersection, all the roads are controlled by stop signs, and vehicles approaching from all directions are required to stop before proceeding through the intersection. In this situation, the design of the in-vehicle traffic light system is based on a first-come, first-served strategy. Thus, the priority to proceed is decided by the order in which vehicles arrive, without other biases or preferences.
Conclusion:
For the application of in-vehicle traffic lights at signal-controlled intersections, unnecessary and disruptive braking and accelerating was significantly reduced in the predictive mode, and it can be concluded that the predictive mode clearly promotes sustainable driving practices.
For the application of in-vehicle traffic lights at non-signal-controlled intersections, the in-vehicle traffic light significantly improved the post-encroachment time and decreased the maximum brake application, which implies that driving safety was enhanced.
Team members:
Bo Yang
Research Associate, Institute of Industrial Science, The Univ. of Tokyo
Kimihiko Nakano
Professor, Institute of Industrial Science, The Univ. of Tokyo