Simplify round-trip routes

[samcrawford]

Some round-trip routes end up with many many waypoints shown, leading to overly complex routes that would be hard to follow.

Possible options:

• Don't cross the route (probably infeasible) or penalise it
• When selecting waypoints to route around a green feature, have a maximum waypoint density - e.g. 1 per km. There is currently no waypoint density limit

Example: https://trailrouter.com/#wps=51.54804,-0.02541%7C51.63373,-0.00381%7C51.63708,0.00042%7C51.63673,0.00414%7C51.63728,0.00127%7C51.63970,0.00201%7C51.64132,0.01066%7C51.63755,0.01374%7C51.64005,0.02244%7C51.63499,0.02571%7C51.63406,0.03323%7C51.63124,0.03170%7C51.63105,0.03229%7C51.63105,0.03229%7C51.63312,0.03371%7C51.63177,0.03646%7C51.63818,0.04068%7C51.64314,0.03870%7C51.64637,0.04211%7C51.64317,0.03853%7C51.64807,0.03657%7C51.64265,0.03262%7C51.64884,0.03384%7C51.65028,0.02250%7C51.64281,0.01145%7C51.64344,0.00012%7C51.64517,0.00444%7C51.64412,-0.00090%7C51.64371,-0.00090%7C51.64350,-0.00554%7C51.64352,-0.00117%7C51.64335,-0.00221%7C51.64053,-0.00084%7C51.63613,-0.00665%7C51.63565,-0.00248%7C51.54804,-0.02541&ss=&rt=true&td=40000&aus=false&aus2=false&ah=false&ar=true&pga=true&im=false

[samcrawford]

Another possibility for the avoid repetition feature: right now, avoid repetition simply tries to avoid running on the same path twice. But there could be another path adjacent to the original one and it'd happily use that. Perhaps avoid repetition should set a distance buffer around the edges already visited and then avoid entering that buffer.

[samcrawford]

Notes to self...

Main cause of lines crossing / complexity in routes is when routing around green polygons combined with the avoid repetition option.

Example: https://osm.trailrouter.com/#wps=51.45005,-0.07347%7C51.44806,-0.07755%7C51.44855,-0.08269%7C51.44615,-0.08282%7C51.44378,-0.07913%7C51.44440,-0.07512%7C51.44245,-0.07772%7C51.44145,-0.07034%7C51.44806,-0.07755%7C51.45005,-0.07347&ss=&rt=true&td=5000&aus=false&aus2=false&ah=false&ar=true&pga=true&im=false

Things to experiment with:

• Simplify the green polygons. Convex hull is an option.
• Turn off avoid repetition for polygons?
• Improve avoid repetition to look for nearby edges, not just exact matches.
• Turn off avoid repetition for the initial out-and-back to the green feature (first and last waypoint). Will be a nightmare to then edit routes afterwards.

While investigating, disable trail and water routes (done), disable fallback, disable duplicate removal and removal of routes that are too short/long

[samcrawford]

Some improvements made and released, but still lots to be done. Changes made:

• Bugfix: Avoid Repetition does not consider the first and last edge in a segment.
• Be more tolerant of low speed roads. We now do not penalise roads with <35km/h speed limits. Anything over that gets a heavy penalty still (unless it's specifically ok for foot traffic).

Convex hull work looked promising. Modifying avoid repetition to look for nearby edges is very inefficient, need to find a better way of handling this.

Putting back on hold for now.