Navigation Bug in 2004 (2005(?)) Prius Nav

I can't explain why it would prefer a longer and slower route but some of this depends on how you set the defaults for the different levels of highways/streets. If there is a large difference between main road and highway speeds, then it will bias the fastest selection to what it considers highway routes. While I would consider US101 is a major highway, it's hard to say how the Nav would classify it since it has many sections that are not controlled access and have cross traffic. If you want to change the calculation, you can adjust the average speeds it uses for major streets and highways under Menu/Settings.
FYI - when I route to my brother's place in Santa Barbara, the Quick1 and Shortest routes are about the same at 295 miles going down US 101. The Quick2 route goes out to I5 and is about 425 miles, but takes <strike>only slightly longer that </strike> about an hour longer than Quick1.

Edit- must have been asleep when I posted last night. Actually I calculate a significantly longer time on I5. See the more detailed information I will post below.

 

<div class='quotetop'>QUOTE(efusco @ Jan 29 2007, 01:56 AM) [snapback]382206[/snapback]</div>

My problem is typically trying to keep me on the interstate, even though an alternate route (which would be 50 mph) is at least 30 miles and 30 min. shorter. I'd be traveling slower on the interstate in that area than on the bypass.

Dave M.

 

<div class='quotetop'>QUOTE(aforkosh @ Jan 29 2007, 12:28 AM) [snapback]382200[/snapback]</div>

I tried some different default speeds but with my south bay location, but I can't reproduce your problem. There may just be too much distance difference between US101 and I5 for me. Even by bumping the highway speed up to 70 mph, I couldn't make I5 come out quicker. The 3 speed options and default speeds that I have are residential (25mph), main street (35) and highway (55). I normally bias highway up to 60mph but if it is set much higher, it want's to take me out to the freeway for just about every local trip I make. The fact that it would select a slower "quick" route is strange. What exactly are the 2 quick and slowest route calculations you get for your Oakland-Santa Barbara trip?

 

Be advised that US101 switches back and forth between freeway and non-freeway many times between the Bay Area and Santa Barbara. (A freeway must have on- and off-ramps; if there are side roads and intersections, it can't be a freeway.)

This causes the Nav to compute the US101 travel times using a mix of Freeway and "Other Highway" speed values you entered in its Setup menu. Since the Nav must make a route decision before you start moving, it uses these speeds as its best guess for time enroute.

Therefore, the Nav comes up with an all-freeway time on I-5 that's quicker than US101. That's because it assumes you're slowing to the non-freeway "other highway" speed on portions of US101. Naturally, you won't slow down, but it doesn't know that.

Also, the Nav may make the "quickest" decision based on a few minutes' difference, which is trivial to us.

(You can see US101 displayed in two different colors along its length, showing its change from freeway to highway.)

 

<div class='quotetop'>QUOTE(aforkosh @ Feb 5 2007, 11:32 PM) [snapback]385947[/snapback]</div>

Another post provides some additional insight on this. If the built in road speed information can actually reflect the true travel speeds on I5 then it could easily become the recommended route when compared to speeds appropriate for many sections of US101. The ETA calculations using the less detailed main street and highway speed numbers would not accurately reflect this variation.