RESULTS: INCIDENT VERIFICATION

Athens Results (On-Line Incident Verification to test performance of IV Call Center)

Athens Results (On-Line Incident Verification by WAP)

Athens Results (On-Line Incident Verification for IV WAP Version 0-2)

Incident Verification Summary

The Incident Verification system was tested at the Attiki Odos site that was opened recently to the public. This complicated the deployment of the test because of the prevailing low traffic conditions. The following observations were made for various traffic conditions necessitating a careful design of the site tests to obtain meaningful results.

High/low traffic volume situations: under heavy traffic automatic incident detection usually performs better, while during low traffic conditions, the IDS will be more dependent on manual means of detection;

Day/night operation: night operations will pose challenges on the monitoring and detection of incidents. As visibility is reduced during these periods, manual means of detection, such as patrols, might be intensified;

Lanes/shoulders incidents where detection by an automatic system might not be feasible.

A mathematical model provides the means to design the site tests for traffic volumes between 400 and 2000 veh/hour.

The basic idea is that incident verification would not proceed until the original call is confirmed by others calls from drivers on the motorway. However, the traffic manager needs to know how many calls to expect for an optimum deployment of an incident verification strategy. Possible strategies can range from less stringent (i.e., one driver call with low detection time), to very stringent (i.e., more than two driver calls with high detection time). This is where the conflict resides. Stringent strategies are accurate but not effective since they usually require a very high detection time. On the other hand less stringent strategies are not very accurate but are effective since they require a smaller detection time. Obviously the adoption of an optimum strategy requires a mathematical model relating all the fundamental traffic parameters that influence the verification process such as:

• The number of vehicles (drivers) entering the incident visible zone (independent variable).
• The probability of a driver with a WAP mobile phone reporting an incident (dependent variable).
• The probability of a driver possessing a WAP mobile phone (constant parameter-threshold).
• The traffic conditions reflected by the traffic volume V (veh/hr/lane) (constant parameter-threshold).
• The detection Time (t) (dependent variable).

The targeted Measures of Effectiveness (MOEs) for the IV module are the following: