Criminality spread: a "Boomerang effect" of public transport improvements?

The relationship between accessibility or the degree of improvement of urban transport and criminality has been underestimated and close to forgotten. This paper aims to reveal the importance of public transport policies in the evolution of crime configuration in a city. The hypothesis that the probability of transport improvements in a zone depends on some of its socio-economic characteristics is adopted. The use of the propensity score matching technique reveals that the presence of improvements of public transport in a zone of the city has a direct and significant impact on the increase of some types of crime. Likewise, spatial econometrics results expose that crime tends to be contagious in neighbouring zones. The presence of the Transmilenio system in Bogota may share out criminality to other zones of the city. Negative externalities like the better mobility of offenders and, then, their possible choice to expand their criminal activities to new zones, can spoil the positive effects of enhancement of public transport. Far from suggesting no developing public transport or isolating some "dangerous" neighbourhoods or inhabitants, this article shows that improvement of public transport may not only generate positive externalities; policy makers should take into consideration the mutation and shift of criminal behaviours in order to identify possible solutions such as the construction of more establishments providing health, welfare and sporting activities, as is evoked in the results. In this way, the "boomerang effect" of the improvement to transport will be reduced.