| Title | Percentage of driver journeys delayed due to traffic congestion |
Associated Targets | Reduce the proportion of driver journeys delayed due to traffic congestion |
Brief Description | This indicator monitors drivers' own perception of whether or not their journeys by car were delayed due to congestion, regardless of the journey type or the nature of the roads they travelled on. It is not an actual figure for time lost due to congestion ( e.g. as in Transport Scotland's Congestion on Scottish Trunk Roads publication). |
Strategic Objective(s) to Which Indicator Relates | This indicator informs progress in relation to the Wealthier and Fairer Strategic Objective. Reductions in congestion enable shorter and more reliable journey times. This contributes to improved productivity and economic growth. |
More Detailed Definitions | |
Definitions of Keywords | The figures are produced from survey information about journeys (or stages of journeys) that were reported as having been made as the driver of a car or a van. In each case, the interviewer asks "was this part of your trip delayed due to traffic congestion?" No definition of traffic congestion is given, so respondents can interpret the term as they wish. |
Evidence Source | Scottish Household Survey ( SHS), Travel Diary Percentage calculated from survey responses All else being equal, the smaller the percentage who say they were delayed by congestion, the more efficient and reliable the road transport network is. It is a proxy for efficient, reliable transport networks as no single measure is available to capture overall performance. |
Baseline and Past Trends | 2006 baseline value of 12.8%, an increase on the 2005 figure of 11.8%. Data was initially collected in 2003 and has increased in 2 of the 3 years since. |
Methodology for Data Source | Each year's figure is based on a sample of around 14,000 journeys reported by car drivers. On the basis of the SHS's standard estimates of sampling variability, the 95% confidence limits around the latest change is +/- 0.9 percentage-points. However, the Travel Diary results may be subject to greater margins of error than this. |
Data Ownership and Quality Assurance | National Statistics |
Publication of Data | The latest data appears in Scottish Transport Statistics (Table 6.9). http://www.scotland.gov.uk/Topics/Statistics/Browse/Transport-Travel/PubScotTrans 2007 data is not yet available due to issues with the data. It is expected to be published in Summer 2009. |
Methodology for Recent Change Arrow on Scotland | This evaluation is based on: any difference within +/- 0.9 percentage points of last year's figure suggests that the position is more likely to be maintaining than showing any change. A decrease in the perception of delays of 0.9 percentage points or more suggests the position is improving; whereas an increase of 0.9 percentage points or more suggests the position is worsening. |
Future issues or reviews | A change in the way in which the Travel Diary was structured means that 2007 data has been delayed whilst quality assurance checks are being carried out. This will be made available in Summer 2009. |