Going to the Zoo: A comparison of travel time ratios in 21 European cities

Efficient public transport is an essential component of a sustainable transport system. The travel time ratio, i.e. the public transport journey duration divided by the car journey duration of the same trip, can be used to compare the public transport system with the road transport system within and across cities. However, few studies have used the travel time ratio to analyse the efficiency of the public transport system across European cities. The aim of this study was to compare travel time ratios of a typical leisure trip across 21 European capital cities and to examine the association of journey time and travel time ratio with socio-demographic characteristics of cities. For the purpose of this study trips to the local zoo were selected as a leisure time activity that is comparable across cities in Europe. Within 21 European capital cities random start points were selected based on an 8 km service facilities analysis from the zoo. For each start point to zoo trip the duration and distance of the public transport and car journeys was calculated using the Google Maps Directions API. Our analysis showed that in all cities public transport journeys take longer than car journeys, with a mean travel time ratio of 2.61 (range 0.98–5.82). No correlation was found between public transport and car journey duration, suggesting that they are influenced by different factors. However, mixed model analyses found no association between socio-demographic characteristics of the cities and public transport journey times. In contrast, mixed models showed that a decrease in the travel time ratio was associated with a larger population size, higher population density, higher percentage of working population, more urbanized land area and more registered cars. To encourage a modal shift towards sustainable urban transport, we recommend that travel time ratio should be considered in the design of public transport and car infrastructure in cities.