Motorways, urban growth, and suburbanisation:evidence from three decades of motorway construction in Portugal

Portugal moved from having less than 200 km of motorways before joining the European Union in 1986 to having the fifth highest motorway density relative to population in the Union in 2017. This paper studies the relationship between the expansion of the Portuguese motorway network between 1981 and 2011 and the growth of population and employment in the 275 mainland municipalities of the country. We address the endogeneity of the geography of motorways using instrumental variables based on historical transport networks from 1800 and 1945. Our findings suggest that, on average, new motorways caused large increases in both population and employment. In line with existing evidence for other countries, we find that motorways contributed to suburbanisation, as the impact of motorways on population growth (but not on employment growth) is particularly strong in suburban municipalities. In addition, motorways also appear to have influenced urban agglomeration dynamics, as their effect on population growth depends positively on the municipality’s population size in 1970.