How do I predict future traffic flows from available ...

1 Review and Assessment Helpdesk, March 2010 How do I predict future traffic flows from available counts and what part does TEMPRO play? Guidance for England and Wales English & Welsh Regional traffic Growth and Speed Forecasts English and Welsh Regional traffic Growth and Speed Forecasts (RTFs) provide the basis for scaling forward traffic flow data within England and Wales. These forecasts provide both national and regional growth estimates for the country. Air Quality Consultants Ltd has published an Automated traffic Growth Calculator for England and Wales which provides growth factors derived from the RTFs.

2 This calculator can be obtained here (v. 3-1). The original RTFs, published by the Department for Transport, can be obtained from: +/ The RTFs are divided by vehicle class and are provided for a range of area types (large urban, other urban, inter urban, rural and all areas) and road types (motorway, trunk, principal, minor and all roads). If it is unclear which of these area or road types is most appropriate to the area of interest, and there is no local advice available from colleagues, it is suggested that all areas or all roads is used as default. RTFs provide national and regional data, which do not focus upon local levels.

3 Since traffic volumes are likely to grow at different rates in different localities, it is necessary to refine the RTF factors. TEMPRO provides the data required for this local adjustment. TEMPRO TEMPRO takes account of local planning data to provide factors which, when used in conjunction with national or regional traffic growth forecasts ( the RTFs), can provide very local traffic projection factors. It is important to note that TEMPRO should not be used on its own to provide growth projections. It should always be combined with national or regional forecasts. The TEMPRO programme and guidance for its use are available at For instructions on how to download and install the programme see the bottom of this note.

4 NB. TEMPRO data do not apply in Northern Ireland. How to Perform the Calculations This section describes how to perform the calculations. A worked example is given at the end. Step 1 Download the Automated traffic Growth Calculator for England and appropriate datasets for TEMPRO from the links given above. Step 2 Follow the instructions provided with the Automated traffic Growth Calculator for England in order to obtain traffic growth factors for the desired future year. Factors are provided for a range of vehicle classes and for All traffic (for use when traffic splits are not available in the original data).

5 Step 3 Open the TEMPRO Programme. The front page of TEMPRO has two windows; Datasets available and Chosen Datasets . The Datasets available window should contain a number of regional datasets downloaded from the TEMPRO website (see end of this note for instructions on downloading these datasets). Click on the desired regional dataset and drag it to the Chosen Datasets window, and click Proceed to Selection Screen under the Actions tab. On the Selections Screen ensure Trip Ends by Time Period is selected in the Trip Purpose box. Under Area Definition select Geographical Area and click Edit , which will take you to a new screen.

6 Place a tick in the box next to your region, then expand the + symbol next to this box. Find the precise area (or areas) that is/are most appropriate for your data and place a tick in the accompanying boxes. Exit this screen by selecting Return to Selection Screen in the Actions tab. Ensure that All purposes is selected under the Trip Purpose Definition box, and under Time Period highlight Average Day . In the Base Year box, select the year during which the traffic was counted, and in the future Year box, select the desired future year. In the Transport Mode box, ensure that only Car Driver is ticked, and in the Trip End Types box select the Origin/Destination button.

7 Click on Proceed to Results Screen under the Actions tab, which will generate an Origin and Destination growth factor for the selected region and area(s). Average the Origin and Destination factors for each to calculate a Regional TEMPRO factor and a Local TEMPRO factor . Step 4 Adjust the RTF factor obtained from Step 2 for local growth derived from TEMPRO, as follows: RTF factor x (Local TEMPRO factor / Regional TEMPRO factor) = Final Growth Factor Step 5 Multiply your original traffic flow data by this final growth factor to calculate future traffic flow data.

8 Worked Example For a location in Nottingham, you have total vehicle flow in 2005 of 10,000 vpd (AADT) and wish to predict the flow in 2008. 1. Nottingham is located in the East Midlands region and is best described as a Large Urban area. Using the Automated traffic Growth Calculator for England , select 2005 from the Base year drop down menu, and tick the Area box. From the drop down menus select East Midlands under Region , and Large Urban under Area , then click GO . This gives an RTF factor for All traffic in 2008 of 2. Using TEMPRO, ensure that the correct selections are made on the Selection Screen and calculate a Regional TEMPRO factor, using East Midlands ( EM ) as the region and a Local TEMPRO factor, using Nottingham(main) , which is the most appropriate area in this case.

9 This gives a growth factor between 2005 and 2008 for East Midlands of (average of Origin and Destination factors) and similarly for Nottingham(main) of 3. Finally, the RTF factor from Step 1 can be adjusted for local growth derived from TEMPRO to give a final local growth factor, as follows: RTF factor x (Local TEMPRO factor / Regional TEMPRO factor) x ( / ) = The final local growth factor is thus 4. Multiply your flow in 2005 by this final local growth factor: 10,000 x = 10587 vpd Guidance for Scotland, Wales and Northern Ireland RTF data are only provided for England, and thus for traffic flows in Scotland, Wales and Northern Ireland, the previous method for scaling traffic data with National Road traffic Forecast (NRTF) factors should still be applied.

10 Air Quality Consultants Ltd has published an Automated traffic Growth Calculator for Scotland, Wales and Northern Ireland which provides growth factors derived from the NRTF factors. This calculator can be obtained here. The original NRTF factors, published by the Department for Transport, can be obtained from: +/ (Table 2A) The NRTF factors are divided by vehicle class and are provided for a range of growth levels (low, central and high). If it is unclear which of these growth levels is most appropriate to the area of interest, and there is no advice available from colleagues, it is considered that central growth is likely to be the most appropriate selection.