track size on interactive map

Im designing shiptracks on an interactive map(openstreetmaps) (see example image). there is a distintion in size and color to indicate what type of track and what kind of size the track is. But now i'm thinking about how could i define what the minimum size of a track should be and what te maximum size of a track should be?

Being able quickly and accurately select a track is important, but then again it's also possible that there are a few hundred tracks in close range of eachother, so i can't make them too big.

Anyone has any suggestions for me how to have a rationale for the choice of the size?

Really appriciate it!

Thanks.

Alec