The task aims at building a multi-level control of the traffic in large urban transportation nets. The basic unit we operate with is the traffic microregion. It is a logically delimited collection of crossroads and the communications joining the crossroads. We suppose, some of the crossroads are controlled by signal lights and the arms of the controlled crossroads are equipped by detectors -- measuring devices, providing us with transportation data (intensities and densities of the traffic flow).

The basic variable we model and control is a vector of queue lengths that are being formed in the arms of the controlled intersection. The queues are approximated by the number of vehicles, using the physical principle "the increment of the queue is given by the difference in the amount of incoming and outgoing cars". In addition to this, a linear dependence of the car density measured on the remote detector on the column length is considered. In this way a state space model for queue lengths and density in the microregion is constructed.

The controller built on the basic of the presented model has three levels:

1. Local control which cares of a single microregion, only. It predicts column lengths of the microregion (which are no measurable) and computes ratios of the greens for signal lights, so that the columns would be minimal. The estimation is performed by Kalman filtering, for the optimization is used linear programming.
2. Coordinating control cares about the "good relations" between the microregion. With no coordination, the microregions incline to overload their neighbors, if convenient for them. The coordination prevents this phenomenon. Both the model and the optimization are just slight modifications of those from the local control.
3. Exceptional states control cares about the states of the traffic, which do not belong to the common transportation. They are e.g. accidents, closures, big over-saturations etc. They are supposed to be described by discrete model and through them, mostly control using the collected expert knowledge will be realized.

The traffic control algorithm based on these principles has been developed in cooperation with ELTODO EG and finalised and practically tested in cooperation with ELTODO dopravní systémy.

Currently we are in the process of extending the model and improving the controller in the scope of a project NOMŘÍZ, a joint effort of ÚTIA, ELTODO dopravní systémy and Czech Technical University, Faculty of Transportation Sciences.

Contact:

• Jan Přikryl
• Jitka Homolová
• Ivan Nagy

Projects

• Ministry of Transportation of the Czech Republic, No. 1F43A/003/120,
• Ministry of Education, Youth and Sports of the Czech Republic, No. 1M0572 (Centre of applied research DAR ),
• Technology Agency of the Czech Republic, No. TA01030603 (NOMŘÍZ).

Local SVN repository (accessible with password only):

http://mys.utia.cas.cz:1800/svn/doprava