A causal model relating urban form with daily travel distance through activity/travel decisions

Urban form is often assumed to influence travel distance. However, as this is no travel choice in itself, but the consequence of other decisions, this paper tests, consistent with the activity-based approach, a causal model that does not relate urban form directly with daily travel distance, but indirectly through a series of decisions. A structural equation model was developed with urban form measures for both the residential and the work environment. The model demonstrates that indirect effects can steer a total effect in another direction, indicating that the apparent effects of one variable on another can be the trade-off of opposite effects. Effects from residential density suggest that people in a dense residential environment travel a little less, although this effect is partly cancelled out by extra activities. Workplace density/mix increases total daily distances, but decreases distances by car.