Higher speed is identified as the main cause of mobility growth, operating on the principle that when people travel faster, they inevitably cover greater distances. This dynamic serves as a concise summary of passenger mobility history, illustrated by the 1981 opening of the high-speed rail connection between Paris and Lyon, which enabled daily commuting between the two cities for the first time. Similarly, the post-World War II rise in car ownership and speed facilitated increased travel distances to workplaces, schools, shops, hospitals, and social gatherings.
Data from the Netherlands indicates that the average daily travel distance per person tripled between 1960 and the present, rising from 10 to 30 kilometers. This growth is attributed entirely to car usage, which offers faster door-to-door travel compared to public transport or bicycles. Empirical studies support the conclusion that total travel time remains roughly constant at an average of 1.1 hours per day; therefore, when travel time is fixed, higher speeds inevitably result in longer trips.
Despite this evidence, conventional wisdom among traffic engineers and politicians often overlooks the dominance of speed, instead citing rising incomes, decreasing driving costs, remote work trends, or shifting preferences as the primary causes of mobility growth. This omission obscures critical consequences for transport policy. First, building new roads in congested areas fails to solve congestion in the long term. While initial capacity increases reduce traffic and boost speeds, these gains disappear within a few years as extra capacity attracts additional traffic, a phenomenon described in studies such as "The Fundamental Law of Road Congestion."
Secondly, mobility growth will cease once average car speeds stop increasing. This reality is already evident in wealthy nations with mature motorway grids. In the Netherlands, average car speed has stabilized since the turn of the century, leading to a 3% decrease in per-person car mobility between 2005 and 2019. Similar declines have been observed in the UK, Spain, Belgium, Sweden, and Luxembourg during the same period. Ignoring car speed as the main driver leads to traffic forecasts that are systematically too high.
Finally, cars in large cities travel at less than half the speed of the national average, meaning metropolitan citizens drive half the distance of those in other areas. Urban environments feature shorter trip distances, nearby destinations, and a significantly higher share of public transport compared to rural regions. Consequently, urban density that mixes housing, workplaces, shops, and parks offers the most cost-effective way to improve accessibility while simultaneously reducing car use.
Arie Bleijenberg, President of T&E, concludes that these misconceptions favor vested interests in the car and road industries. By neglecting speed as the primary force behind mobility growth, policymakers are hindered from implementing effective strategies for affordable and sustainable accessibility.
Sources: CleanTechnica.