How to show direction traveled on a map?

I have a map with locations coming from a user. Sometimes these are sparse (1 location every 500 meters), and sometimes dense (many locations every 100 meters). I have them plotted on a map, similar to this:

However, in my application, they aren't always paths from A to B. Sometimes it is the person leaving home, going for a drive and then coming back again. This causes the route to basically be a circle (sometimes the route home is the same as the route out, but they don't overlap exactly - different side of road). I'd like to be able to show the direction travelled on the map.

One option is to draw arrows, but that isn't always possible. Consider this:

If I'm in a dense region, then I'll either draw many arrows, and they will overlap and be very messy. Alternatively, if I draw no arrows in dense areas, there may be a very long distance between arrow draws.

Are there best practices for this type of thing? An app that shows direction travelled particularly well?