Check speed for linking water to roads

[abyrd]

It seems like we're still linking faraway cells to roads with minimal or no cost. This should be changed with a shorter linking distance and lower speed to traverse any >1 cell links.

[abyrd]

We appear to still have this problem wiith driving searches. There are still big horizontal jumps in isochrones at the coastline (see image) which imply zero travel time.

[abyrd]

This might just be an illusion caused by the car being relatively fast. Still should be checked in the code to make sure speed is being properly applied.