Journey Time: So, Just How Long Does It Take to Drive the A9?



Journey Time: So, Just How Long Does It Take to Drive the A9?

Authors

Stephen Cragg, Transport Scotland, Douglas Gilmour, TomTom Global N.V

Description

Travel times form a key component of the appraisal, modelling, monitoring and evaluation of road investment projects. But what is meant by journey time and does the approach to data collection matter?

Abstract

Travel times form a key component of the appraisal, modelling, monitoring and evaluation of road investment projects. But what is meant by journey time and does the approach to data collection matter?
The A9 is nearly 300 miles long connecting the Central Belt of Scotland to the North Coast of the mainland and thus to the ferry terminus to the Orkneys and Shetland Islands. At around 100 miles long, the section of the A9 between Perth and Inverness is a combination of single and dual carriageway. In the short-term, to help reduce accident numbers and severities, an Average Speed Camera system will be installed on the single carriageway section along with a pilot scheme to increase the speed limit for HGVs from 40 to 50 miles per hour (from ~65 to ~80kph) .In the longer term, this section will be upgraded to dual carriageway.
An important question posed as part of the appraisal of these projects is “So, just how long does it take to drive from Perth to Inverness and vice versa”.
On the face of it, this seems like a simple question but in a world where there are now multiple ways to collect or harvest the data to answer this question, the need to understand precisely what data is being captured becomes all the more important. Whose data is being captured, are they ‘typical’, what do outliers represent, how is the data cleaned?
The first part of the paper reports on the work undertaken by Transport Scotland over the period 2007 to 2013 covering the different answers obtained from a number of different sources of journey time data including moving observer, ANPR, Bluetooth and ‘third party’ services considering the good, bad and unknown elements of each (i.e. provenance, practicality, coverage, quality).
The second part of the paper presents the work undertaken by TomTom to rise to the challenges set by Transport Scotland.

Publisher

Association for European Transport