Which of the following is a geographic concern that would play the biggest role in planning new transportation infrastructure

a) Traffic patterns and congestion in urban areas

b) Elevation and topography of the terrain
c) Proximity to water bodies and natural obstacles
d) Population density and distribution in the region

All of these factors are important considerations when planning new transportation infrastructure. However, the geographic concern that would likely play the biggest role would be population density and distribution in the region. This is because the level of population density and the distribution of people in an area would directly impact the demand for transportation and the potential routes that need to be established. It would help determine the need for new roads, highways, or public transportation systems, as well as the optimal locations for these infrastructure projects.