A comparison of headway and time to collision as safety indicators

Publisher's full text

The two safety indicators "headway" and "time to collision (TTC)" are discussed and compared with respect to their usefulness in determining the safety of different traffic situations, like different locations in a junction. Over a 6-day-period traffic flow measures were taken in a four-way junction with stop signs on the minor road. It was found that for vehicles in a car following situation headway and TTC are independent of each other. The percentage of small headways is relatively constant across different locations in the junction, while the percentage of small TTC values varies between different locations. It is recommended to use headway for enforcement purposes, because small headways generate potentially dangerous situations. TTC, on the other hand, should be used when a certain traffic environment is to be evaluated in terms of safety, because it indicates the actual occurrences of dangerous situations.

LATEST NEWS


2017-11-30

Millions for research into maritime transport and the environment

Maritime transport is a major source of emissions of harmful air pollutants and carbon dioxide. In a new project, a research team from the Swedish National Road and Transport Research Institute (VTI) and the University of Gothenburg has received SEK 6.4...


2017-11-30

New research programme for more efficient travel

The Swedish National Road and Transport Research Institute (VTI) is playing an important role in a major new research programme to find radical solutions leading to fewer trips and more efficient travel, along with tools to enable better use of roads and...


2017-11-30

Simulator used to practice emergency responses safely

Emergency responses of the police, ambulance, and rescue services are associated with a high risk of accidents, but practicing them in real traffic is neither safe nor permissible. A simulator-based method developed by the Swedish National Road and Transport...


2017-10-26

Simulation of cut-in by manually driven vehicles in platooning scenarios

A study in a VTI-driving simulator has showed that a platoon will be able to handle a cut in from a manually driven car. The results of this study have recently been presented at two conferences in Japan.


2017-10-16

ERPUG Forum

The five-year anniversary of European Road Profile Users' Group (ERPUG) Forum will take place at Ramboll head quarter, Copenhagen, Denmark October 19-20, 2017.


2017-09-29

Self-driving buses in Sweden next year?

A self-driving, fossil-free bus. This idea might become reality through a forthcoming collaborative project involving the Swedish National Road and Transport Research Institute (VTI), Linköping University and several other participants. The project group aim...