How can it chose 2 different routes?

[Germs]

How can it be my sat nav will often take me somewhere via 1 route but return me via another - why would it chose differently depending on whether you are coming or going?

[marshalla]

Couple of reasons

a) it is receiving traffic info. and routing you away from congestion
b) the routes are almost the same length, but when reversed the longer one become the shorter for some reason.

[Germs]

Not a) but possibly b) - thanks for your response.

[sgrimshaw]

Which Sat Nav?

Some will plan different route based on time of day.

[mrmr96]

I bet the difference is marginal, and possibly caused by the sat nag expecting process at different rates in opposite direction on a road. Probably to do with the level of traffic using the road in each direction, and how roundabouts and junctions work with other busy roads.

I.e. You'd probably find the driving along the route one way, vs the reverse journey DOES take longer, and the sat nav planning reflects that, by choosing the quickest each time.

[New POD]

Germs said:

How can it be my sat nav will often take me somewhere via 1 route but return me via another - why would it chose differently depending on whether you are coming or going?

It's very sensitive. I drive from L37 to DE24 each week. It tells me to travel along the M58 to the M6, but when I join the M57, at it's junction with the M58 is adds just one minute to the expected time.

Then it expected me to leave the m6 at Junction 15, but if I leave at Junction 16 it looses a minute.

I assume that it's got it in it's head that a motorway is better than a dual carriage way