Overview
The project identified two areas for further research. The first involved the processing and review of existing storage theory and their implementation in practice, the second included the field trials and the study of the effects of traffic information.
Main goals of the project were:
To determine the impact and benefits of traffic information storage time instead queue length; to develop guidelines for the determination of traffic jams; and to determine the criteria for the application of this traffic information.
The study had to be limited to two field trials, both of which had a high proportion of urban transport. In these field trials it was possible to bypass the traffic jam driving on surrounding roads.
From the field trials comprehensive data were generated, so that an in-depth evaluation and analysis was possible. The findings provided a basis for the introduction of traffic in line-up on high-performance roads.
Funding
Results
The research project on "queuing time instead of queue length" handled the relationship between the type and content of traffic information and the behaviour of road users.
The causes and relationships involved in the forming of queues have been known for a long time. The traffic queue begins when the volume of traffic before the bottleneck is greater than the bottleneck's dis-charge capacity. Other factors include the composition of the traffic streams, local conditions, visibility etc. The most suitable models for the calculation of queuing times and journey time losses are macroscopic models which illustrate the traffic flow, since the initial data (traffic volume, average speed) can be recorded by various detectors.
The project suggests a simple algorithm which is sufficiently adequate for planning purposes, and which can be used to calculate the lost time.
The findings concerning traffic information on lost time are of particular interest for the research work. Field trials were used to investigate the changes in behaviour of road users, and the results assessed to derive recommendations for the use of such information.
Traffic information on queuing time - that is, the journey time including the waiting or lost time for a particular section of road – enables a better estimation of travel time in contrast to dealing with details of queue length. The following conclusions can be derived from the field trials:
- Roadside, "on-trip" traffic information about queuing situations led to increased re-routing onto the lower level road network, compared with situations where this additional information was not available. For this reason, preliminary local field trials using variable message display panels are necessary in order to investigate the effects of the above.
- The traffic information has no or only very little effect where the values for ‘queue length' or ’queuing time’ are low.
- The change in behaviour here is strongly dependent on the size of the queue as provided by the traffic information. The information on existing increased queuing conditions for the investigated road sections led at times to diverted trips of up to 25% of the total traffic.
- The effects of the traffic information cannot however be applied to other situations, but are dependent on the particular situation in each case and on the availability of alternative routes.
- For identical queuing conditions, the information on queue length