The role of the traffic signal is to manage traffic to reflect the priority policy among the various travel modes and travel directions. The design logic of traffic signal plans is complicated by the wide variety of situations that it needs to handle. Due to this complexity, the programming process cannot be carried out as an optimal mathematical process, therefore an integration between quantitative models and engineering considerations is required.
The programming process must consider the entire life cycle of the signal design, which includes the following stages:
- The initial plan, which is carried out by the engineer and should reflect the pre-defined design policy.
- Examination of the plan by the authorities to verify that the planning policy was properly implemented.
- The ongoing adaptation of signal plans to ensure their fit to the dynamic mobility patterns.
Thus, a signal plan design system ought to include quantitative and logical algorithms that enable effective implementation of all these stages.
INBAR is a signal plan design system developed by the TMRC for the Ministry of Transport. It is the standard system for signal program design in Israel.
INBAR reflects the design standards in Israel, while accounting for developments and the experience gained in traffic engineering, travel modes and computing technologies. The design and examination processes embedded in it provide tools to assist decision-making within the design process and to incorporate quality assurance and design guidelines.
INBAR integrates various unique computational and examination processes. Examples include:
- Algorithms to develop the flowchart of the design and calculation of the minimal cycle duration for every branch, while maintaining safety constraints.
- Algorithm to calculate decision points for the branches, taking not account the interaction between branches.
- Identification of cases of illegal skipping of phases in the flowcharts.
- Comparison of alternative channeling in low-data designs.
- Comparison of alternatives in green wave designs, including an ability to integrate performance measures for passenger and public transportation vehicles.
The design data are exported to form a basis for interfaces with other systems. An example is the interface that was developed for receiving programming data from the traffic management and control system AVIVIM.