Introduction This paper analyses six years' data from the People and Places longitudinal study. The study examines travel behaviour impacts of major investments in active travel infrastructure in three Outer London boroughs (the ‘mini-Hollands programme’). Methods A controlled longitudinal analysis was used to compare changes in active travel in intervention and control groups, with three levels of intervention group (mini-Holland borough but no local intervention; active travel infrastructure but no low traffic neighbourhood; low traffic neighbourhood, usually also with proximity to active travel infrastructure). Finally, the article estimates the 20-year health economic benefit from uptake of active travel, using the average point estimates across all waves for both the mini-Holland programme as a whole and in the most intensively treated areas. Results At all waves, living in an area with mini-Holland interventions was consistently associated with increased duration of past-week active travel, compared with the control group. Changes in active travel behaviour were largest and had the strongest evidence for those living in low traffic neighbourhoods. Most of the increase was in time spent walking, although the strongest evidence of increased participation was for cycling. There was also evidence of decline in car ownership and/or use, although this was weaker and seen convincingly only in the low traffic neighbourhood areas. The 20-year health economic benefit from the mini-Holland areas was calculated at £1,056 m, from a programme cost of around £100 m. The most effective interventions (low traffic neighbourhoods) provide a twenty-year per-person physical-activity related benefit of £4800 compared to a per-person cost of £28–35 (LTNs implemented during 2020 as Covid-19 emergency interventions) or £112 (higher-cost LTNs with more features like greening and crossing improvements). Conclusions Active travel interventions provided high value for money when comparing health economic benefits from physical activity to costs of scheme implementation, particularly low traffic neighbourhoods. |