IQ routes and posted speed limits

[Uncle Tom]

So far it seems all posted speed limits are 60 MPH! Are the speed limits logged on the maps considered when figuring routes? If so there are many side streets/city routes that's showing the defaulted 60 MPH when it should be 35 MPH or other.

I have been working feverishly updating speed limits on streets. Hopefully it will help with accuracy with both time displayed and routes it decides.

Any thoughts about this?

 

[dhn]

Default speed limits are imbedded in the map data when route calcs are made. What made this unreliable for NA roads, prior to IQ routing was that, for NA roads, TomTom had three default settings: Highway, Main Road and side street.

European maps had 6 or 7 road types, each with an associated speed.

However, IQ routing takes into consideration 'real world' data as drivers go on the roads. So, if the default speed limit is, say, 35 mph but data shows drivers REALLY drive it at 50 mph (IQ2 considers the time of day in the factor as well), then with IQ routing, fastest will map a route and consider that road X can be driven at 50 while, if IQ routing data shows road Y really being driven at 40, then routing will select road X, even if both roads, by default are 35 mph.

Make sense?

 

[Uncle Tom]

Default speed limits are imbedded in the map data when route calcs are made. What made this unreliable for NA roads, prior to IQ routing was that, for NA roads, TomTom had three default settings: Highway, Main Road and side street.

European maps had 6 or 7 road types, each with an associated speed.

However, IQ routing takes into consideration 'real world' data as drivers go on the roads. So, if the default speed limit is, say, 35 mph but data shows drivers REALLY drive it at 50 mph (IQ2 considers the time of day in the factor as well), then with IQ routing, fastest will map a route and consider that road X can be driven at 50 while, if IQ routing data shows road Y really being driven at 40, then routing will select road X, even if both roads, by default are 35 mph.

Make sense?

Yes, and if NO IQ routing exist for that road, does the defaulted posted speed limit take into effect?

 

[dhn]

That is my understanding, yes.

 

[mvl]

When you turn off IQroutes, the Tomtom reverts to road class. In my experience, the speed limits you enter are totally ignored, always.

The only value I have found in entering speed limits is to enable the "over speed limit" alert.

 

[gatorguy]

MVL, check something if you don't mind. Are there roads that IQR assumes travel faster than the posted speed limit. In other words, everyone breaks the legal limit on that road and IQR assumes you will too? I don't have either of my TomTom's available for the next couple of days.

 

[dhn]

If mvl doesn't get back to you, gator, I'll check for you later today.

But, I presume that's how it all works. Otherwise ETA's would wind up based upon default speeds for the roads, not real world stats.

Anyway, I'll do a demo route later if you still need the info.

 

[mvl]

MVL, check something if you don't mind. Are there roads that IQR assumes travel faster than the posted speed limit. In other words, everyone breaks the legal limit on that road and IQR assumes you will too? I don't have either of my TomTom's available for the next couple of days.

Yes, I've seen it by looking at arrival time estimates. If I drive 70mph flow of traffic on a 55 mph, the arrival time doesn't move. If I drive 55 on a 55, the arrival time increases.

You can't see this on a route demo. Probably for liability reasons, route demos only run at IQspeeds if the road has no speed limit loaded. Once a speed limit is loaded, the demo will run at the posted speed. But it still sets arrival times and routing based on the internal IQ2.

 

[canderson]

MVL, check something if you don't mind. Are there roads that IQR assumes travel faster than the posted speed limit. In other words, everyone breaks the legal limit on that road and IQR assumes you will too? I don't have either of my TomTom's available for the next couple of days.

Absolutely! I posted something to that effect here a few days ago.

I was "buzzing" down I-25 on a Sunday afternoon a week and a half ago. Was surprised to see that while over the limit by a significant amount, the ETA was NOT being reduced. It was clear that the IQRoutes already knew that the average speed on that section of road was above the limit at that time of day on a Sunday. I couldn't buy back a single minute from my original ETA. ETA turned out to be right, too.

 

[mvl]

Oh, and to reiterate my point from a few posts earlier:

I deliberately set some roads at 120mph and /or 10mph, in an attempt to impact routing. With IQroutes enabled and disabled, those speed limit changes had no effect.

This is why I conclude that speed limits only affect the "Over the speed limit" alerts, and the route demo speeds. Nothing else.

I don't bother with mapsharing them any more. I update errors in my neighborhood, but don't add any.

 

[doctormstein1]

speed limits

you guys are probably right but I am getting a slighly different view. If my unit says 45mph on one road and I go faster then this I do pick up minuits so with me on long island ny it seems that the iqroutes is working and adjusting somewhat to the speed limit in my unit and actually how fast I am traveling

 

[canderson]

you guys are probably right but I am getting a slighly different view. If my unit says 45mph on one road and I go faster then this I do pick up minuits so with me on long island ny it seems that the iqroutes is working and adjusting somewhat to the speed limit in my unit and actually how fast I am traveling

It could be that the average speed on the day and at the time of day you are driving is right around the speed limit. You can certainly lower your ETA if you go fast enough on any road, but it may require going over the speed limit by more than a little to do it if nobody else pays it any attention either!

It would also be necessary for TT to have valid IQ data for it or it would use the default speed, if it knew one. I assume it's at least showing an accurate speed limit?

Speaking of your neighborhood, I was out on the L.I.E. with my 720 a few weeks ago and found that moving (ahem) somewhat faster than "suggested" by the signs (this was at about 10:00pm at night after a late arrival at LaGuardia) the ETA wasn't improving. Then again, I wasn't passing anybody, either, so it's probable that the TT knew what the real average speeds would be. That same weekend I also had reason to cross back over and make a fast run up the Bronx River/Sprain Pkwys and found the same thing. Pretty consistently 10 over, and I think I gained only 2 minutes over the entire run.