how i would create a heatmap with lines of where I have been with esri software
1)split line at vertices
2)add unique id field, calculate
3)feature vertices to point (mid-point)
4)Generate Near Table (took over 2 hours)***over 13 million records; only allow nearest 25 within 100 feet
5)run frequency on input values
6)join data/ tables back together and choose the colors you want – voila!