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Renewed accessibility indicators for road network municipality of Groningen

For the accessibility of the municipality of Groningen as a whole and the economic core areas in particular, the roads that connect the municipality with the region, province and the rest of the Netherlands are very important. In order to provide a better insight into the quality of the road network, the municipality developed new accessibility indicators together with partners. These are criteria on the basis of which the quality of the accessibility of the municipality is measured.

Accessibility of economic core areas

The municipality of Groningen has been working data-driven within the mobility domain for some time to provide insight into the quality of the road network for car traffic. This regular monitoring provides relevant information, for example for ad hoc analysis at route level for projects, for testing and validating traffic model results and as input for the budget and policy accountability.

Especially for the latter, the municipality was looking for a highly simplified representation of the quality of the accessibility of the five economic core areas: UMCG, Martini Hospital, city center, Zernike and Europapark. The aim was to be able to give a score for ‘Traffic flow’ and ‘Reliability’ for each core area.

Traffic flow and reliability of the road network

For these accessibility indicators ‘Traffic flow’ and ‘Reliability’, the municipality uses the travel time information about the road network for car traffic available at the National Road Traffic Data Portal (NDW). The municipality translates this information into monthly reports, in which the quality of the network is mapped for a large part of the main road network for each direction of travel in both the morning and evening peak periods.

In order to reduce the large amount of data on the various routes, driving directions and rush hours to two scores, the municipality has investigated a number of methodologies together with Arane Adviseurs. Ultimately, a method was chosen that properly reflects the situation on the street, that offers room for ambition and growth and that is easy to explain.

Norm values and target values

The calculated values for the ‘Traffic flow’ and ‘Reliability’ are compared with predetermined reference values. The first reference is the norm value. This expresses the minimum desired quality. If the value does not meet the standard value, there is a bottleneck. The score is then determined on the basis of the difference with the standard value.
Target values have also been calculated in the same way. The target value indicates what is maximally possible on a route with the current layout and equipment.

Terry Albronda, Smart Mobility policy developer at the municipality of Groningen explains: “We can now examine from year to year per economic core area how the quality of accessibility is developing. It also provides insight into where bottlenecks are still present and what room there is to implement improvements. The scores give a good first impression and with all the underlying data many detailed analyzes can be performed.

Koen Adams, project leader at Arane Adviseurs: “Although the data is widely available, there are relatively few road authorities who use the data in this way for policy monitoring. The municipality of Groningen has thus opted for a progressive approach that is in line with the network vision and provides good insight into the (development of) network quality. Besides the strategic application for budget planning, tactical and more operational applications are also conceivable. The monthly overviews also provide insight into day-to-day differences, which makes it very useful for evaluating events or road works.