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Union Street Pedestrianisation - Traffic Modelling

Aberdeen City Council have previously commissioned consultants to construct a paramics microsimulation traffic model of the city centre called the Aberdeen City Centre Paramics Model (ACCPM). This model was used in providing analysis of proposed infrastructure test runs. The testing and modelling work has been carried out on a staged basis. This iterative process of testing allows the effects of displacement to be taken into account when identifying what infrastructure improvements will be required.

Issues identified

The ACCPM testing indicates that as a result of the committed developments occurring by 2006 the resultant capacity problems on the current city centre infrastructure will become more pronounced, with delays through Market Street, Guild Street and around the central core. Over time these conditions will continue to deteriorate. Current conditions show that car park provision is adequate, yet under-utilised in a number of locations. Driver behaviour suggests that a large number of cross-town trips are made to access car parks in the central core. Signing at these car parks is poor and inadequate, with excessive queuing experienced.

The immediately required infrastructure to aid a resolution in some of these existing locations are an improved signing strategy and the implementation of a Variable Message Signing (VMS) strategy for car parks. This would also assist in improvements to the traffic movements around Guild Street/Wapping Street gyratory. Although not a final solution, it would give almost immediate impact. With these immediately required measures, local congestion issues will still occur and in particular traffic from Torry will still have trouble crossing Victoria Bridge due to congestion at the existing roundabout at North Esplanade West. Further infrastructure improvements would therefore be required.

Closing Union Street at this point creates delay problems for the re-routed public transport services on both Schoolhill and Guild Street. This in turn causes safety concerns at Schoolhill in particular where there is a significant amount of conflict between vehicles and pedestrians. Implementation of bus priority measures on both Schoolhill and Guild Street will mitigate delays to public transport and may improve the pedestrian environment between the two existing shopping centres. As a consequence two possible east/west routes are therefore removed. Improvements to the Market Street/Guild Street junction are also required as currently competing movements cause the road network to queue excessively and in many instances gridlock occurs.

Infrastructure measures

In order to provide sufficient capacity across the road network a series of complementary infrastructure measures have been identified in order to accommodate the interchange between north/south and east/west traffic at suitable locations. These measures would provide a clearer route definition throughout Aberdeen City Centre with specific corridors catering for the travel demand whilst other areas are given over to public transport and pedestrians. These proposals will assist in providing for, not only the Union Street pedestrianisation, but also the future Urban Realm vision for the city centre. Alternatives for Union Street pedestrianisation scheme (between Market Street and Bridge Street) have been investigated, e.g. restricting movements to bus and taxi only, or widening the footways to restrict traffic to 2 lanes. It is considered that the effects on the road network from the implementation of these partial measures would still require large infrastructure improvements.

Results of the Traffic Modelling Process

Consultants have been working to build a City Centre traffic model - the Aberdeen City Centre paramics model that replicates the individual vehicle movements around the City. The following images show levels of congestion for various scenarios during the pm peak period in 2006.

Test 1 - Images

Testing has been carried out to establish the level of congestion expected in the City Centre in 2006, when many committed developments (that are known at this time) become operational. The following "snapshots" show the level of congestion that is likely to be experienced in the city centre in 2006.

Base Network - Overview
Base Network - City Centre (North)
Base Network - City Centre (Central)
Base Network - City Centre (South)

Test 2 - Images

Union Street was then closed (between Bridge Street & Market Street) and the tests were re-run. The "snapshots" shown at this stage demonstrate the levels of congestion that is likely to be experienced in the city centre in 2006 with the closure.

Base Network with Union Street Closure - Overview
Base Network with Union Street Closure - City Centre (North)
Base Network with Union Street Closure - City Centre (Central)
Base Network with Union Street Closure - City Centre (South)

Test 3 - Images

The final test images show the road network with the Union Street closure and all the infrastructure improvements in place. The "snapshots" demonstrate the potential improvement in levels of congestion that could be achieved in the city centre in 2006 with the improvements in place.

Improved Network with Union Street Closure - Overview
Improved Network with Union Street Closure - City Centre (North)
Improved Network with Union Street Closure - City Centre (Central)
Improved Network with Union Street Closure - City Centre (South)

Comparison Image

The final image compares the two possible scenarios with the closure of the section of Union Street between Bridge Street and Market Street. The images remove the background road network and show only vehicles, which gives a clearer impression of the queuing traffic. The image on the left is with the Union Street closure on the existing city centre road network and shows a significant level of congestion. The image on the right shows the potential improvements in congestion levels that could be achieved with improvements to the road network. It demonstrates the potential of vehicles being able to move more freely on a road network that can cope with the increased demands of the city centre traffic and the pedestrianisation of Union Street.

Comparison between Base Network and Improved Network

Contacts

  • Transportation Strategy and Programmes
    Planning and Sustainable Development
    Aberdeen City Council
    Business Hub 4
    Marischal College
    Broad Street
    Aberdeen
    AB10 1AB
    Phone: 01224 522618
    Fax: 01224 523180
    Email: programmes@aberdeencity.gov.uk