Traffic Modelling

At PDC we build and apply highway models and assist clients with their own scheme identification and appraisal. Following previous attempts at producing regional highway traffic models, our reputation has been enhanced by our innovatory database approach to successfully building two very large regional traffic models for the Highways Agency covering the east and southeast regions. They have been linked together to produce an inter-regional traffic model and are being used for scheme development and appraisal. We have also developed their ERICA and ERNEST database software.

Here are some brief details about some projects we have conducted in this area.

Eastern Region Traffic Model

Date: 1991 to 1995

Peter Davidson Consultancy was appointed as co-consultants with Colquhoun Transportation Planning to build the Eastern Region Traffic Model (ERTM). The ERTM covers most of the DOT Eastern Region stretching from Cambridge in the North to the M25 in the South, and from Oxford to the East Coast. It has been particularly useful to plan and provide forecast data for the various scheme consultants assessing the traffic effects of highway proposals in the region for the next twenty years.

During the project, we developed the database approach to transport models whereby the major data sources were put into a modeling database from which different models could be build. These databases would be used as a comprehensive tool to maintain and update the regional model and to provide a consistent set of base data for local scheme studies within the region. They were designed to interface and to SATURN, TRIPS and COBA. These databases have been the basis for most of the other models in the region over the last ten or so years. Network data for the Eastern Region was originally based on the DfT's Network Information System (NIS) and subsequently refined and supplemented with more detailed data as it became available. New data was obtained from county councils in the region, from local traffic studies and surveys commissioned especially for ERTM. As part of the project PDC was commissioned to develop database software, which would hold both highway network (ERNEST) and origin-destination matrix data (ERICA) for the whole region.

The model is a major detailed model with some 748 zones and 5,811 links in both TRIPS and SATURN with connection to COBA. The origin-destination matrices were built using the databases and the model validated for the base year 1991. The model was distributed in whole and in parts to various scheme consultants throughout the region. This was a major modeling study with attention to detail and precision.

The model was linked to the South East Region Traffic Model (SERTM) and the combined model had over 1000 zones and over 10,000 links. The matrix building procedure led to major developments in techniques and software and led to further development of SATURN so as to take account of particular features of long distance trips.

South Eastern Region Traffic Model

Date: 1992 to 1995

Following the success of the database approach developed for ERTM, Peter Davidson Consultancy was asked to assist WS Atkins with the South East Regional traffic Model (SERTM) covering all of the South-east England south of London and extending as far west as Southampton and Oxford.

The amount of data available for the SERTM was greater than that for the ERTM. Some 1200 RSI stations (including transposed sites) were used in matrix building compared to 800 sites form the ERTM. This presented a more complicated and challenging modelling problem. Matrices were successfully built and validated in SATURN initially for the all day period for all vehicles. Subsequently, matrices were built for the peak and inter-peak periods for several different market segments based on vehicle type and trip purpose and assigned in SATURN.

PDC was also centrally involved in building a combined ERTM/SERTM model of the complete South and East regions in SATURN and TRIPS which had over 10,000 links and over 1000 zones.


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