Don't the newer Edges do precisely that? At least when used in conjunction with RWGPS? [disclaimer - I've never used an Edge /]
I've seen several references to using an Edge in this mode, in this forum. I assumed they display routing hints embedded in the Track comments tags (so yes - not map-derived, not directly anyway), which gives the illusion that they are 'routing'. Most other GPSs simply ignore this embedded information.
So built up, sure different roads, countryside not a major issue.
Well I'd see that the other way around - being led down different roads in a built-up area is rarely a problem, its just one of 2 parallel routes less than 100m apart. Taking an 'alternative' route in a rural area on a bike can result in you cycling several kilometres out of your way.
For this reason I like routing in 'Delivery' mode (only available on older GPSs
) in towns because it tends to take you off the trunk roads, but that same mode outside of towns is a very bad idea, because it's indirect and that's not good when your next junction is 5km away ...
Out of towns, or with a newer GPS which has more limited options, I'd just use 'car'.
What's a good free mapping tool that I can use to create a simple gpx route?
I've tried the export route option on ridewithgps but it creates a turn-by-turn route which blows the 50/100 routepoint limit on the hcx.
I know I'm repeating myself here, but part of the problem is indiscriminate use of the word 'route'. Most planners are just like RWGPS in that if you export a 'route' you get a broken file much as you describe (and all Garmins have low routepoint limits, not just the old Etrexes). For this reason most people who use planning tools end up exporting a Track, which is much more likely to work, in its own rather dumb way.
But a Track is not supposed to be a navigational aid, that is the job of a Route (either 'direct' or 'follow road'). Nearly all the planners are dysfunctional in this regard.
I don't know about RWGPS but its easy to get the kind of Route you want in BikeHike for instance, simply by turning off the 'follow road' option before you start planning. The problem now of course is that you can't see the planner choosing the right roads for you on screen. But that doesn't actually matter because as Kim points out, unless its the same map (which it usually isn't) and the same routing algorithm (which it never is), all bets are off anyway. All you can do is use plenty of points (but within your limit of 50). 50 points should be OK for a day's riding, but if not then simply create multiple shorter Routes, because the GPS can store 50 of them.
To be 95% sure that the routing will go where you want, yet conserving the number of points you use, try clicking on 'every other' road you want to use (rather than every road) and as Kim says, avoid placing the points on junctions, or close before junctions - 200m or so
after each junction works much better, if your GPS is operating in 'follow road' mode. The reason for this is that you don't want anything to interfere with the GPS/map-generated messages that appear during the approach to a turn.