A computer calculates the trips.

They buy the data on what roads exist, where they are, what direction they (if one way, for example), the speed limit, etc.

Then computers use some very complex route selecting algorithms to predict the most efficient route. Thousands of routes may quickly be evaluated (gross oversimplification) for a given request and they won't always get it right.

In this case, since Mapquest did give the right route (Google Maps switched between the one I linked to and the one you gave depending on the exact address in Orange used as the destination), it just screwed up the description of the path through the 5/22/57 interchange and I suspect that is a defect in the vendor data, not their own.

The directions mapquest gave you are technically correct. There interchange there has lanes on the right that allow you to exit onto the 5N, or the 57N, or, stay on the 22E. It's just having you go through those lanes rather than stay to the left.

That's what I figured out, but was so strange to me that I figured it had me on the trasition road for a transition. Why make it so difficult for the public??

As Alex said, it's not a conscious decision, it's a programmatic quirk.

The way these route-calculating algorithms work (in very simplified terms) is that every road, every turn, every transition is assigned a weight that indicates a relative "cost" of taking that route over another. Assigning that weight is a complex process, and that's what Mapquest pays those providers for. So for whatever reason, in the data the Mapquest buys, those transition lanes carry a lower "cost" of travel than the freeway-proper.

Knowing that transition well, as I drive it nearly every day, it could be that the average speed along the transition road is faster than the average freeway speed. Or it could be that it might cut out a few dozen yards of driving distance. Or some other combination of the many factors that go into those value assignments.

The thing is, the exercise of driving-route-optimization is a highly complex and nigh unsolvable problem in the world of computer programming. There is actually no way to solve perfectly without requiring an amount of processing power that grows exponentially with the number of routing options. So these programs are forced to take shortcuts and make assumptions. They're pretty good at it, but there will inevitably be some holes in the logic. Google maps is sure to have its share somewhere. Though of course gmap's on-the-fly route changing features make them a little easier to account for when they do happen.

Ok, well then it isn't an issue of the underlying data but rather the logic of the computer.

I would guess this happened because the route described is slightly shorter than just staying to the left on 22 and so far as it knows all other things are equal (speed limit primarily) so it is technically the faster route. But I couldn't say for sure.

OT: Keep reading the thread title is "Why is Mapquest so sticky?"

Just sayin'...

:D I read the same think when I came back to it....and I wrote the dang thing!

Knowing where you live I thought you'd have some insight on the local part. Because of all the work on the 22 I have been driving from Brookhurst up Chapman all the way past the 55 to our Dr.s office. Now that the work is done I thought I'd try the freeway.

Great info on how this works. It seems like the quirks happen for me more often than not....

In my experience, Mapquest seems to have these weird quirks more than Google Maps

But at least with google maps you can manipulate the the trip to change it to meet your needs.

Anyway, I suggest checking a map like Thomas guide to verify the directions before leaving.