26 June

TfL Ultra - Low Emission Zone Stated Preference Research


In February 2013, the Mayor of London announced his intention to create the world’s first Ultra Low Emission Zone (ULEZ) in central London with the aim of ensuring all vehicles driving in the centre of London during working hours would be zero or low emission from 2020. The key objective of the present research was to gain an understanding of how current road users of different types in central London would be likely to respond to the ULEZ scheme upon its introduction, and how sensitive their responses would be to a range of scheme variations.


The study involved the use of two stated preference surveys: one aimed at owner-drivers (which included cars, small vans, LGVs and HGVs) and one aimed at fleet operators of LGVs and/or HGVs. The owner-driver survey was conducted online, and the fleet operator survey was conducted via telephone. The final sample contained 1,155 interviews.

The owner-driver survey questionnaire was designed around the use of two stated preference exercises:

  • The first choice exercise focused on the decision over whether or not to replace one’s main vehicle with a compliant vehicle if the ULEZ scheme was implemented.
  • The second choice exercise was asked only of car and van drivers, and focused on what the respondent would do, for up to three specific journeys into the Congestion Charging zone that they had made recently, if the ULEZ scheme was in operation and they had a non-compliant vehicle.

The fleet operator survey was also designed around two stated preference exercises:

  • The first exercise focused on the decision over how many of the non-compliant HGVs and LGVs currently operated by the respondent would be replaced with compliant vehicles if the ULEZ scheme was implemented
  • The second exercise focused on how many journeys would continue to be made in non-compliant vehicles given the introduction of the ULEZ scheme.


Results from the stated preference surveys showed the proportion of vehicles, both owner-driven and fleet-operated, that would be Ultra Low-compliant by 2020 in each scenario. Additional outputs included the elasticities of response to the ULEZ charges.