1. Congestion is not a fate F.Wittwer
IMPACTS/ ZAGREB / MAY 08
Congestion is not a fate
F.Wittwer

2. Definition of congestion
Congestion is due to a disruption of the level of service because of imbalance of supply and demand in relation to space of roadway system and space time

3. Definition of congestion
Congestion grid systems are the consequence of a disruption of capacity of the network, in space or time.

4. Definition of the capacity
The capacity of a network is defined by a level of service (speed, safety, etc) allotted to the various means of transport.

5. Causes and effects of congestion
the incomplete realisation of the plans of displacements which create disruption of the level of service for various means of transport

6. Causes and effects of congestion
the inconsistency of policies of regional planning and transport which generate imbalances of offers and requests in time (peak hours)

7. Causes and effects of congestion
the deficiency of safety requirements in the realisation of installations creates more and more incidents which reduce the capacity in time

8. Political and technical objectives in order to limit congestion and its effects
the solution of a durable reduction in congestion consists of defining clear political matter objectives of sustenable development, relayed by quantified technical objectives (PT speed, rate of accidents, rate of pollution, etc) which makes it possible to evaluate the evolution within the framework of an observatory.

9. Political and technical objectives

10. Tools available to reduce congestion
The tools used to reduce congestion (construction of infrastructures, ITS systems, urban tolls, etc.) are often contrary to the reduction of congestion in the medium term. These tools should not be used within the framework of “reactive” processes, strictly - in response to a problem of congestion, but within the framework of a process of prospective sustenable development.

11. Method to ensure durable effects of the actions
the most popular method to avoid congestion is a realisation of a project carried out according to principles' of quality assurance (principle of mutual valorization of the projects) by avoiding the realisation of the projects according to only criteria's of political acceptance or financing which create situations of disruption of level of services.

12. Recommendations
It is recommended that the general principles of durable development apply systematically in any realisation of projects. It recommends that planning is accompanied by a control program of project on the basis of quality plan in order to avoid the negative impacts of isolated projects.

13. CONCLUSIONS
I am convinced that congestion is not a natural phenomenon, that it can be controled durably by good prospective project management and not by using the usual tools in a reactive manner which, badly used, always appear to generate congestion.

14. THANKS
F.WITTWER SG IMPACTS
MAY 2008