Zumo Routing Question

On this weekends Welsh National Rally, my Zumo 346 took me down this https://goo.gl/maps/kdZ9VYeL9MwXfwCM6 , single track, mud/grass in the centre road, rather than the more obvious, quicker A479 south from Talgarth?

Route Calculation set "Faster Time"



Any ideas why?

The mud grass lanes in wales are often classified as national speed limit. The south west peninsula rally is the same. Using base camp you can zoom right in and check any corner cutting by cross referencing with google street. Been caught a few times but it's an adventure and part of the memory. Cracking rally this year and the weather was really kind.

My Zumo 350 (set to fastest route and no unmade roads) took me down something similar from Llanbadarn-Fynydd to Abbey CwmHir. It probably was the fastest route given how far I'd have has to ride to find an easier route. These devices do seem to like an absolutely literal interpretation of the instructions given to them, which is why basecamp is worth persevering with.

Thanks Guys, yes I'd thought it was down to speed limit allocated to each road. As fantic says, adds to the adventure

The answers are entirely correct.

The Garmin algorithms rely on the known data for each road on the map. Garmin rely on third parties to supply that data, for obvious reasons. For instance, if Garmin’s map data tells the algorithm that a one mile stretch of road A to B is a 30 mph limit it will route the rider along it in preference to an alternative road of say 1.5 miles A to B that is also a 30 mph limit. If the algorithm does not know that the 1 mile road is a cart track, where the rider would be lucky to make 10 miles an hour is beyond the algorithm’s control.

You can see the same effect in towns and villages where the algorithm will create a diversion to cut a corner as it is 100 yards shorter (and therefore ‘quicker’) when the sensible option is to ignore the instruction to cut the corner (down a side street) and ride to the next crossroads instead. Sometimes you just have to be cleverer than the dumb machine on the day..... and check the route before you set off!

I didn't have any great routing problems on the Welsh National this year, though have had some bonkers lanes chucked at me on the SWPSR. All great fun, whatever