Network Performance Measures

We worked with the Department for Transport to develop the Public Service Agreement (PSA) targets for both urban areas and the Strategic Road Network (SRN) of motorways and ‘A' roads managed by the Highways Agency. In addition to assisting with specifying the measures and the implementation process, we evaluated the data sources to be used for setting the targets and for monitoring progress.

In a separate linked project with the Highways Agency, we have a technical role in developing the Highways Agency Traffic Information System (HATRIS) used to implement the process of calculating the PSA journey time reliability measure and monitor the performance of the Highways Agency network. HATRIS is a database which aspires to hold the best estimate of journey speed and traffic flow for every 15 minutes for each of the approximately 2500 main carriageway junction-to-junction links of the network. Data from September 2002 onwards is held in the database.

The HATRIS database is of importance to the Highways Agency. Accurate flows and speeds are used in project design, environmental and traffic/economic analysis, roadwork planning, and congestion monitoring. The PSA journey time reliability targets can only be set and monitored by using a database of traffic flows and journey speeds and hence accurate HATRIS data is essential.

We're involved in all stages of the processing of the data needed to generate the outputs required for the PSA targets and monitoring other Highways Agency requirements. These stages consist of the following:

• evaluation (characteristics and statistical accuracy) of data sources derived from disparate technologies, including Motorway Incident Detection and Automatic Signalling (MIDAS) inductive loops, Automatic Number Plate Recognition (ANPR) and GPS (Global Positioning System) data
• specification of processing algorithms to remove invalid data, transform the data and generate the required outputs
• data-fusion algorithms to combine data from the disparate sources into the most reliable estimate of journey speed
• Quality Assurance testing of the implementation of the processes by the Highways Agency database contractor
• process documentation and general support to Highways Agency users of the HATRIS outputs.

These tasks require a wide range of skills including database design, software design, statistical analysis, scientific research and documentation of processes.

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