IQ Routing

[DavidS777]

Another TT user had a post discussing the routing of his TT device. And I had some comments which I gave...

But, I'm new to TT, and they're just my thoughts. But, the question got me to thinking on it; so this is just a generic post on IQ routing. Learn a lot here reading - on the history, etc - about the gps devices.

If a TT device has IQ routing - you can't turn it off. Any route which it gives you - is going to have IQ influence.

Any alternate route will have IQ influence. IQ routing is part of the programing of the device. Can't get away from it. (But why would you want to??)

I have read (here at this great forum) people asking for a choice between Garmin or TT. Questioning which has better maps. And DHN or MVL replying that essentially - all the maps are equal. Depends on where you are. A specific area that you are looking at, or comparing. I live in Seattle. Maybe the TT map is better in Seattle, than Garmin. But maybe in Chicago - the Garmin is better than TT.

People put the maps together, and all of that. Lots, and lots of roads. We have the round-about turn issues, etc.

So, the Historic data which is being used for IQ routing - will be better or worse - for a specific area. Just as the maps are. And the device is using the maps to develop a route - so it should be expected that IQ routing quality will vary with the specific area where the device is being used.

I've lived other places. But I grew up in Seattle, and am living here now. Very familiar. Today, out and about - I did a small, simple test. I know how the TT always likes to route me down this long freeway - and I turn off of it way before it wants me to - for various reasons. My TT is set for 'fastest'.

Today, I changed it to 'shortest'. TT promptly routed me off the freeway. Then it did something totally unexpected. Rather than have me go down a long stretch of road, and then turn here, and go down this long stretch, etc... It did something I truly did not expect.

It had me make a turn, and then make another turn; and then go a short stretch and make another turn....

When I consider what it was doing - it was doing a 'step' like process. Which will definitely end up being the SHORTEST route to my destination (my home.) But absolutely not the fastest. But, I wasn't asking for the fastest. My priority was SHORTEST. A computer has no intuition. Something shorter by 5 feet - is shorter by 5 feet. By constantly moving me in short increments - on one road heading North; and then another short section heading West - it was basically attempting to get me moving in a Straight line towards my house. Lots of turns, and not efficient. And not intuitively any type of route which a normal person would take - but definitely a 'short' route.

Now, within all of these parameters - of 'two stepping' streets to my home - the IQ routing also existed. It has to - because it is part of the program. So, it is also somewhat two stepping based on traffic. But since it is taking a ton of side streets, not really a lot of traffic info. But it would use what it had...

Cities are great for IQ. Lots of historic route info. Rural areas have less roads; and less traffic - so IQ routes would not be as effective. Less roads to deviate from; and less historic data as well....

Before the IQ route development - I don't know if a TT device on 'shortest' would have created a 'stair step' route - trying to create a straight line, and a road - where no road or straight line exists. For me - with numerous roads in Seattle, it quickly becomes evident - that the 'shortest' setting is useless. Great for education on how the TT is routing; but not much else.

But, with all of this; no matter what your setting - IQ routes are always in every route. With your unit set on 'fastest'; and you request a route - it will give you the best, fastest historic route for your destination. Depending on the data quality of the map for your particular area. And; if you decide that you wish to go a different way; and request a different or alternative route - IQ routing still exists in that alternative route. But from the historic data, number of intersections, traffic lights, hills and elevation of roads, etc. it is probably a slower route.

Now, personally - I don't care! I am absolutely amazed at this small device; and along with the satellites - what has been managed to be accomplished. In the Seattle, area; I mostly use it somewhat as an 'amusement'. I already KNOW where I am. But it comes in really, really handy - if I'm not real close to home, and need to go to a Hardware store for example.

And when I'm on a trip, or going to a business - which I haven't been to before - I follow the route instructions to a tee. I am a person my lovely wife refers to as: "geographically challenged." And GPS units are a really, really neat invention.

David

 

[dhn]

David, you can disable IQ routing. For planning preferences, the first screen shows a IQ routing button. You can disable (or enable) it there.

Further, IQ routing works only with 'fastest'.

The above is for full menued models. The EasyMenu models with IQ routing will always use fastest and have IQ enabled.

 

[sab]

There is something I have always wondered about IQ routes. I will try to ask the question in the most simple way I can.

I head down south from Montreal pretty much every year. So let’s say I leave my home at 5 am and enter my destination as South Carolina which is a good 16 hour drive.

With the original route let’s say I would be driving through Washington at approx 3 pm so it takes me right through on the 95S.

What would happen if I stop for lunch for 2 hours and when I continue my drive I would now hit Washington at 5pm (rush hour).

Does the original route change automatically to the 495?? Would I be better off to restart “Navigate to” at every stop in order for it to be more accurate?

Just curious.

 

[Rick F.]

I would think it would depend on what information TomTom has collected for that time of day.

I remember coming around Wash. DC at 3 PM. It was so congested (no accidents I was told) that we stopped and checked into a hotel. I mentioned the horrendous traffic to the guy behind the desk. He said it's that way everyday Mon – Fri as a lot of Govt worker flex their hours and traffic stats up around 2 PM.

 

[DavidS777]

DHN - thanks for the info. I had missed that the 'IQ' button was a 'button'; and guess was just thinking it advertised IQ routing and hadn't realized that it could be set to disable....

Further, IQ routing works only with 'fastest'.

Are you sure of this?? When I set IQ to 'either disable or enable' - I still am able to have either option - of either fastest; or shortest. Plus, after the warning about safety & historic, etc. (fastest also being safer) [so you shouldn't use shortest for safety reasons either]; I still have the option for showing you a different route if a significantly faster one comes up, etc. PLUS - choosing 'shortest' does not disable IQ (at least from the perspective of the button assignment. Since IQ will still be selected as either enable or disable.)

From your previous comment and info - I do see that I can select 'shortest' AND also make the selection to disable IQ. Just wondering if your certain that selecting 'shortest' - automatically disables IQ. From my brief observation - I would not think so....

Slightly different: When selecting 'shortest' - you get the warning that this is not always as safe. My wife and I have noted a propensity for the GPS to want to route us into Right hand turns; and avoid (if possible) driving across a road without a light; or doing so and making a left turn.... We have commented to each other - that we thought it was a safety issue with TT. Better to have people (in the US anyway) making right hand turns when possible; or being at traffic light controlled intersections. Now, looking at the device (planning preferences) after your (dhn) comments; I see that it also has a remark about safety when choosing 'shortest'.

Sab - I've wondered the same thing. And considered that it is probably better; to redo the planning of the route; if you stop for a significant time period. The routes are based on historic traffic data; time of day; and travel times from users being submitted via HOME. But I haven't seen it 'replan' - if you stop and eat for 1.2 hours or something; the only time it asks is if the traffic gets bad. And it only takes a few seconds to do; and is not going to hurt anything.

And DHN; thanks again for your clarification.

D.

 

[dhn]

From all I understand, yes, IQ routing kicks in only for fastest.

 

[canderson]

David (the OP David, not the dhn David!):

IQRoutes isn't used for "shortest". "Shortest" implies use of the shortest possible distance regardless of other considerations, and the raw map data alone is sufficient for that. There's no need to discuss speed/time (which is all IQRoutes does) when you've requested that your route be based upon the shortest possible distance traveled.

When IQRoutes is disabled, "fastest" will be based upon some information about road type and any known speed limit, and shortest remains "shortest" - the least number of miles to the target.

 

[mvl]

What would happen if I stop for lunch for 2 hours and when I continue my drive I would now hit Washington at 5pm (rush hour).

IQroutes autorecalculates when your estimated arrival time changes by more than 5 minutes. So it would route around predictable Washington DC rush hour in your scenario.

 

[Andy_P]

From all I understand, yes, IQ routing kicks in only for fastest.

IQRoutes isn't used for "shortest". "Shortest" implies use of the shortest possible distance regardless of other considerations, and the raw map data alone is sufficient for that. There's no need to discuss speed/time (which is all IQRoutes does) when you've requested that your route be based upon the shortest possible distance travelled.

I know the established wisdom is that IQ Routing is only used for "fastest" calculations, but I had also noticed that it still says IQ Routing is involved on the summary screen if you do a "shortest" route calculation.
In fact, as the numbers shown are different it certainly seems to be used , if only to adjust the arrival time (obviously there is only one actual "shortest route").

IQ is also apparently making a difference in the OTHER routing options such as "Eco" and "limited speed".

For your perusal, here are a couple of compilations of different route calculations that I did yesterday, with IQ Routes turned on and off.

Test conditions were a Go940 with the SIM card removed (to avoid complications from Traffic incidents), using "Prepare route" from Central London to a randomly chosen minor road in the middle of nowhere near Skegness in the East Midlands.
Each route was cleared before calculating the next one.

The first was for 01:00 am today:

..... and the second for 9:00am today:

You can see that, for these examples at least, having IQ Routing switched on does seem to make some differences to the routes chosen - slight differences at 9am but larger ones at 1am!

I hesitate to make too many conclusions without making a lot more tests and inspection of the actual roads chosen, but what do you guys think so far?

 

[dhn]

I wonder whether LIVE traffic is coming into play somehow, Andy?

 

[gatorguy]

DAvid, my guess is that TT is using IQR even for shortest routing, but only to determine travel times and not route selection.

Try setting up a short local "Fastest" route with few turns. Check the travel time. Then go to "Shortest", but force the route to the same Fastest you were given earlier. Compare the two times. Should show whether IQR times are in play. I think. . .

 

[Andy_P]

I wonder whether LIVE traffic is coming into play somehow, Andy?

Ahead of you there....

I
Test conditions were a Go940 with the SIM card removed (to avoid complications from Traffic incidents), using "Prepare route" from Central London to a randomly chosen minor road in the middle of nowhere near Skegness in the East Midlands.
Each route was cleared before calculating the next one.

 

[DavidS777]

Gatorguy, Canderson, Dhn and others -

Thanks for all the input. But after review, and consideration - I do essentially believe that the initial assessment was correct.

DHN pointed out to me that IQ can be disabled. Very true. Some models I guess - it can not. But, I don't disable it. I use it...

Neither do I worry to much about the route it is giving me; since I'm using it to avoid traffic or to go somewhere that I don't know how to get to...

The question of IQ routing - was a generic one - and how does IQ affect routing. After a few experiments, and some observations made using the TT; I still believe that IQ is involved in all and any types of routing - if it is not disabled.

Some aspects of IQ routing which people tend to ignore - are Safety traffic issues. The TT engineering people do not wish to route people into what could be considered more accident or incident prone routes. So, with all routes - Safety is also considered. Less so with 'shortest'. Which is why you get a warning about safety - when setting a device to 'shortest'. And when one considers the number of turns which 'shortest' requires - it definitely has 'safety' issues...

Gatorguy - I don't know how to 'force' a route. I looked at my 540; and I find 'alternate' etc. and can make it plan a different route; or avoid a section of road; but it doesn't seem real easy to force a route. I know I have seen numerous people on this Forum talking about 'forcing' a route - I haven't previously tried to figure out how to do that...

A suggestion was made to look at a route. I did so. Even drove a couple of them. You can look at the planning yourself if you want - starting from Monroe. Your mileage will vary slightly (probably) because I'm not (not sure totally why) giving out my exact address...

This is going essentially to a very near Home Depot. Located .85 miles from my residence. Very close. I've practically lived at this store. Walked there in the snow. Bicycled there. Drove there. I KNOW how to get there!

The following are the text directions from my TT on how to get to this local Home Depot. Please be aware that the majority of the directions will not get you to Home Depot. Webster is NOT a through street. (Which is one of the reasons I actually drove these routes - cause I'm thinking - you can't get there like this....) But, I wanted to make sure...

But lets disregard the fact that a few of these routes - will not work. Impossible routes. Let us not worry about that; and just consider that Webster is a through street; and look at what TT is trying to do...

Home Depot - .85 miles from 'Home'

[Seattle, WA /Zip 98126 / start from SW Monroe St. & 35th Ave SW]

Shortest - IQ routes disabled

Total Distance: 1.1 miles (5min 45 seconds)

L - 35th Ave SW

R - SW Kenyon St

L - Holden Pl SW

R - SW Holden St

L - 28th Ave SW

R - SW Webster St

L - Delridge Way SW

Arrive Home Depot (left side)

********

Shortest - IQ routes enabled

Total Distance: 1.1 miles (5 min 30 seconds)

L - 35th Ave SW

R - SW Kenyon St

L - 28th Ave SW

R - SW Webster St

L - Delridge Way SW

Arrive Home Depot (Left Side)

*********
Fastest - IQ routes disabled

Total Distance: 1.2 miles (4 minutes 0 seconds)

L - 35th Ave SW

R - SW Holden St

L - Delridge Way SW

Arrive Home Depot (Left Side)

**************
Fastest - IQ routes enabled

Total Distance: 1.2 miles (4 minutes 10 seconds)

(exact same as just above...)

*********
Actual Fastest; and a little shorter than what TT suggests. . .

L - 35th Ave SW

R - SW Holden St

L - 24th Ave SW

Arrive Home Depot (right in front of you/Straight ahead)

OK - so the TT device likes Delridge. Which is a main, traffic light controlled street. You have a storage lane to use from Delridge for your left hand turn into HD.

The most practical direct route would be to make the Left Turn from Holden onto 24th SW. This runs you directly into a customer entrance driveway at the front of the store.

It also takes you down a paved but narrow RESIDENTIAL street lined on one side with a huge apartment complex. Kids are outside playing in this area all the time. Numerous cars. I routinely use this street (about 1.5 blocks long) to get to HD. But, I never drive FAST; and am always on the lookout for balls, and kids. And a few times I avoid it - because if a school bus is on it, or the mail truck - you cannot get through on the street. And have to wait.

So for safety reasons - I can see why TT avoids this more direct route. It might also have something to do - with possibly how the HD address is actually inputed. My route puts you directly almost at the front door. You come in on the customer loading dock area. Delridge puts you way out on the East side of the huge parking lot; and coming into the store parking area.... But if the address is 'located' next to Delridge - and the address is definitely not '24th St' - (but is identified as Delridge) than the TT is also probably trying to get you to Delridge. I haven't tried a set 'this location' and not use an address (or POI) - which might possibly get a person using 24th - not sure.

Now, any two points constitute a straight line. A straight line is shortest. So, on any 'shortest' route - TT is always trying to create a 'straight line' between any two points. It does this in the same way as a CAD program draws a 'straight' line. By using tiny steps. Continual triangles.

I have attached two jpg's to illustrate. One is of a CAD program straight line. I drew this line at a slight angle so that the stepping was visible.

The other is of a triangle. Want to get to point B from point A. Drive in a straight line. What if no road exists which is in a direct straight line between the two points? Make lots of turns - so that you can try and create a 'straight' line. Just as the CAD program has lots of 'steps' in it - drawing a straight line.

This is exactly what is going on with the TT algorithm. Using numerous streets and lots of turns - to try and create a straight line - while at the same time - also attempting to monitor 'safety'. Which is why one of the questions we are asked - in preferences - is unpaved roads.

Holden Pl SW is an unpaved dirt Alley. 1/4 of a block further west - is paved 30th Ave SW. But, you get to make another TURN and get closer to that 'straight' line.... The alley runs between the back sides of various residences. It is truly an alley.

Webster ends above the Apartment Complex. And immediate west of the Apartment complex (which has existed for YEARS) - is a Wet Basin Swamp. Although I think Webster is the street just at the West end of the Apartment complex - so that if Webster did go through - the TT would have you drive right past the HD entrance; past the police station; and turn left onto Delridge; to make an immediate left back into the HD parking lot...

Local knowledge is always (usually) superior to various maps. I am NOT complaining about TT and routes.

Just noting that 'shortest' is always going to try and create a 'straight' line; and Safety is always going to be somewhat programmed in there as well, just with different levels - depending on what your preferences are. And IQ will always be working as well - unless you have it shut off; (disabled) - but functioning under the rules of your preferences - as best it can...

After driving these couple of routes using Webster - (having to stop at Webster of course since it doesn't actually go through) I then drove back in reverse. And almost got beaned by a car traveling NB on 35th as I pulled out onto 35th (making a left). This is because of the building which resides at 35th and Kenyon; and the vehicles parked right up to Kenyon street... As far as I could see - I was clear. So, I pulled out; and there are vehicles coming up to the building... Visibility is very poor - which is another reason why I usually don't go that way. Plus, it isn't very direct. Lots of turns. But the turns do make it Shorter. But it is safer and easier to use Holden - which has a traffic control light at 35 and Holden...

Anyway, these are just my thoughts, and observations.

I have appreciated the comments and your observations.

D.

 

[DavidS777]

I did one more little experiment.

Drove to HD; and marked the HD as a favorite. Using the 'my current location'.

It wanted to name this as "Webster St. SW".

Anyway, at home, asking it to navigate to my 'local hd' (just created favorite) - it now had no problems taking me down 24th Ave SW.

It then wants me to turn Right onto Webster... but that's just cause it doesn't really know where the HD parking lot is...

So - if you read all the various warnings and observed the traffic routing - Safety does come into consideration. However, safety was not the reason why TT was not using 24th. HD's address as being on Delridge was the reason for that one...

Bye! All of this was done on a Sunday Morning by the way.

Wishing all a great and blessed day.

D.

 

[canderson]

It will take a while to sift through all of that routing, but you have stumbled upon a couple of interesting points.

First, in any kind of test of this nature, you want to be certain that the destination is ON a road somewhere, and the correct one at that. Particularly with large stores and shopping malls, etc. that can encompass one or more entire blocks, the address that's being logged for post office purposes isn't always corresponding to the map data in the GPS. It's particularly annoying when there's a large strip mall where all of the businesses share the same street address, and for postal purposes, they 'subdivide' the address by "Unit 300", "Unit B" or some other nomenclature about which the map is completely clueless. Given that this can throw off even the street used to approach the business, it's a bit of a pain. So if you do this run by spec'ing an exact point as your destination, yes, it can make a big difference.

The other thing that you discovered is that your TT knows nada about many parking lots (though I've seen some very interesting exceptions to this). Again, this can be an issue around malls and exceptionally large businesses. Using address-only information, the TT has no idea what the correct approach might be to one of these lots, and simply dumps you off at the projected (more on that another day - addresses are usually approximated over the length of at least one block based upon start/stop addresses for the block) street address location. Might or might not put you anywhere near an entrance to the lot.

Be aware that there are hidden "left turn" time penalties and HUGE "u-turn" time penalties built into the standard routing algorithm that can pop up at any time. It's also necessary to take into account the lack of map understanding about certain left turn lanes that actually exist into lots. These may be special turn lanes set up for entrances that are not recorded in map data (partly because they enter lots that aren't mapped in the first place), and are not available to the TT for routing. Where this occurs, local knowledge will always beat computer routing. But another funny thing can happen as well -- when projecting "shortest" for distance, I do not believe that any of the usual penalties for left turns or u-turns are taken into account. When projecting "fastest", they always are. We've often asked that TomTom provide a configuration button for users to knock out the substantial penalty for u-turns, for example, since often the TomTom has no idea that special lanes have been set up, or that left turn lanes are being permitted for u-turn use. None of that shows up in the map data. Can make a big difference to routing for shortest/fastest.

There's a ton of stuff going on under the hood there. For future tests, I'd try to make a point of avoiding large mall or big box areas, and avoid "points off map" that can confuse the results. Yeah, I know - they're frequently the target destination -- but the state of the art is what it is right now.

 

[GarCor]

What I have found is if I use google maps to plan a route and then convert it to my TT and have IQ routing turned on I get a different route than I originally planed but if I disable IQ routing I get the route I planed in Google maps.

I have tested this by loading the route in Tyre after saving it to TT and this is what I have found with IQ routing.

 

[Andy_P]

Try adding more waypoints to the route, GarCor.
That should help force the TT to make the same desisions.

 

[GarCor]

Try adding more way points to the route, GarCor.
That should help force the TT to make the same desisions.

Ty Andy usually after copying my Google route to my TT there are to many way points for TT to process or at least I have received error messages from my 920 stating that there are two many WP. What I do is open the file with Tyre and delete many of the way points. ( all non essential )

( I am talking about a route that is 500 + miles or so )

 

[Andy_P]

Ah yes... should have mentioned the 48 max steps in a TT itinerary.