I5 in San Diego at Gilman Drive / La Jolla Colony Dr
I was driving up north, but decided to make a stop at In N Out (Damon Ave) - stupid decision being Easter Sunday :lol: .
Thus, Waze recalculated and suggested to make a off-on ramp u-turn at Nobel Drive.
That was odd, because you can do the same just an interchange earlier; namely at Gilman Drive / La Jolla Colony Dr.
I attached the following two screenshot to clarify this problem:
Waze prefers taking the Nobel Drive exit; however, route speeds shows a saving of 4km and 3min by taking the obviously faster option.
Permalink: https://www.waze.com/editor/?env=usa&lon=-117.23628&lat=32.84774&layers=3873&zoom=5&mapUpdateRequest=4278085
Could someone explain to me why Waze gives this odd ‘detour’ over a faster and shorter alternative?
Thanks, Patrick
Patrick, one quick question-- It looks like you were on the ramp from 52 W to I-5 when you recalculated?
That is correct, just about to merge with I5.
It looks like the problem was due to Big Detour Prevention. The segments of I-5 just before and after the off- and on-ramps at Gilman are Alt-named identically: San Diego Fwy, San Diego. This means that the routing off and back on to the Freeway is considered an unnecessary detour.
The trip off and on at Nobel has multiple segments during the off-on routing which do not carry the matching Alt name, and so avoids the extra penalty added for detour prevention. (The detour penalty is not calculated into the numbers we see on LiveMap or RouteSpeeds, but is used in LiveMap and App route ranking.)
Thank you Tony, that is clearing things up!
How is a decision made to ‘release’ such an intersection from a detour penalty, thus removing the alt from one segment, or to keep it intact? I know from experience (i tend to change my mind before i reach home resulting in rerouting such as this one) that the other option at this point is taking the 52/Regents Rd to the east.
I rather choose Gilman over the way longer Nobel option, and even over the 52/Regents option (4 ramps total).