Urban areas’ new congestion targets are far from perfect and should be seen as provisional, given doubts about the reliability of survey data and apparent flaws in the indicator, it was claimed this week.
Officers were urging caution as the Government and local authorities in big cities committed to goals for curbing the time penalties imposed by ever-increasing traffic levels.
Local government was determined to measure the impact of congestion on people – including bus-users – rather than just focus on vehicles, but the indicator is less transparent as a result.
‘It has proved to be far more difficult than either side envisaged,’ said Chris Carter, Nottingham City Council’s transport strategy team leader.
‘These are almost provisional targets, although the DfT wouldn’t say so. They’re going to need reviewing,’ he added, calling for a standard peak period. Some areas that specify a three-hour peak period plan to tap spare capacity in the ‘shoulders’. Nottingham prefers its established radial route surveys to the DfT’s data from ITIS, which gave faster times, partly explaining ‘rather low’ baseline journey times in other areas.
The city strategy for modal change would have a negative effect on the indicator, as former car-users experienced inevitably slower bus journeys, Carter warned. Time-savings for people switching to trams will not show in the indicator, as it covers different routes.
Greater Manchester also identified this perverse effect as one of the problems with the indicator. On congested routes, the disbenefits would initially be offset by time-savings for drivers, but increasing transfers result in diminishing and eventually negative returns. Confidence levels were still being debated, Ray Heywood, transport policy officer at Leeds City Council warned. There were major differences in methodology, particularly for measuring public transport occupancy. ‘We need next year’s data and probably the year after that before we get a handle on this,’ he said.
Despite the caveats, the indicator ‘better reflects reality,’ Heywood added.