Figure 1. Driving Time to Nearest Proton Beam Therapy (PBT) Facility From Census Tract Land-Based Geographic Centroid^a.

^aThe geographic centroid of a census tract is the geometric center of the geographic region defined by the census tract boundaries. If the geometric center lies outside of the census tract or in a body of water, the centroid is given as the nearest point on land within the census tract closest to the geometric center.