Base year trips fall in updated National Transport Model

MODELLING

Base year car traffic down 21%

Base year car traffic down 21%

Updating the DfT’s national transport model has led to a big reduction in trips reported in the 2015 base year.

Consultants Atkins and RAND Europe were commissioned to update and recalibrate the transport demand model (NTMv2R), which is a core component of the modelling framework used to forecast changes in personal travel by all modes. 

Atkins reports that use of version 7 of the National Trip End Model (NTEMv7), rather than its predecessor NTEMv6.2, has led to a large reduction in trips for the 2015 base year. 

“For NTEMv7 there have been some significant changes to  the trip rates based on evidence from detailed analysis of time trends from the National Travel Survey data. This has resulted in fewer trips being forecast per person in 2015 in NTEMv7 than in the earlier NTEMv6.2 datasets. Thus even though the underlying mid-year population assumptions will have changed little, the number of trips occurring in 2015 has fallen about 23%.”

Total trip ends modelled on an average day fell from 104,202,889 using NTEMv6.2 to 79,767,926 using NTEMv7.0.  

Atkins reports that changes to the value of time offset some of the reduction in car trips. Nevertheless, “because of the NTEM trip end changes, the result is still a major reduction in the number of car trips from 42 to 34.6 million trips per average day. 

“In summary, updating the model inputs without any changes to the model calibration the volume of car trips falls by 18% with the amount of car traffic reducing by 21%. This is driven primarily by the reduction in travel demand input from NTEMv7; and masks the increased car driver mode share (43% compared with 40% previously).”

Atkins adds: “Once calibrated, the reductions in car travel seen here will not necessarily still hold and revised 2015 traffic levels and future forecasts will be produced.”

The DfT is expected to release revised road traffic forecasts imminently.