For some time now I have been looking for a good open source way to calculate drive time polygons (i.e., isochrones). Honestly, I was only looking for solutions and not trying to figure out how to do it. Inspired by this python solution (actually, by the idea of using Google Maps to get the drive distance between points and solving an optimization problem), I created a function in R to do this. Note: this is the first of two ways I have to draw these isochrones. This one will only draw convex isochrones.
The entire algorithm with examples follows after the jump.