melelina

Does anyone understand exactly how the new nav system calculates arrival time? My older RX allowed me to set default speeds for different types of road but the newer version in my 2016 RX doesn't have that setting.

The nav system manual (page 109) says that “Travel time and arrival time are calculated based on the average speed for the specified speed limit”.

I thought that meant that the nav system will “learn” what speed I normally drive for every different speed limit and therefore get more accurate over time but the dealer didn't think that was the way it would work. At the moment, it is grossly overestimating my travel time.

Thanks for any additional insight anyone can offer.

AZLexTech

Gen 9 is programmed with the known speed limits for the specified route. It's using those averages.

Don222

You ask an excellent question. If you received any valid responses, I am not seeing them.

I drive a 2019 RX 350. I find the ETA calculation to be totally useless. So bad that it angers me. My Camry allowed inputs of personal average speeds for several road types and produced excellent results.

As you point out the manual makes a statement about average speed that is nonsensical.

lexus does not appear to be using INRIX or other real time data. The calculation is way off while my phone is somewhat accurate. Also appears to not simply use the speed limit for the road section. If that were the case the manual should say so, and calculation would be closer.

possibly Lexus uses the average speed since reset, which is displayed. If this is the case then resetting the average speed once I get to the Interstate should help. This however would ignore different road types that may occur after exiting the Interstate.

Your post is from 2016. I am just asking if you have learned anything new. Thanks

melelina

Although I spent countless hours working with my local Lexus Dealer, after several months the best response that I ever received from them was "head office believes that it is working as designed". Hard to believe that it was "designed" to work so poorly but I gave up..... The other issue we have in Canada is that the system does not give us access to traffic data and construction/detour info. the manual actually suggests that it is available but after questioning that, I was told that the feature is not available on Canadan models.

I also became frustrated enough with the whole thing that it makes me see red, even after all this time. One of the reasons that my next car will not be a Lexus.

mcomer

Former generations of Lexus Navigations required us to change the default City/Rural/Highway driving speeds
to some value closer to our actual speeds. Not abundantly clear as to how or even why to do it, it is easy once
you find the screen. Result was that the ETA was (at least for me) grossly overestimated the travel time.
Highway default value was 55 mph BTW!

Current systems know the speed limits and both display them on screen and utilize them for the ETA calculation.
OP apparently (and I) routinely exceed the limit and thus are still getting a pessimistic ETA although not to the extreme it
used to be.

melelina

My previous Lexus operated exactly as you say and once I made the manual adjustments based on my driving habits, it was surprisingly accurate. The new(er) version uses speed limit info where available but depending on your geographic area, there are a shocking number of roads where the speed limit seems unknown to the Lexus nav system. Where that happens, it appears (although Lexus seems unable to confirm) that it uses some default speed value *(like maybe you recent average?). In my case in Canada, I drive a lot of secondary/rural roads where the speed limit does not display on the screen. The actual speed limit on those roads is 80 KPH (50 MPH) but the nav system appears to use a value very close to 60 KPH (37 MPH) which is results in a massive difference to the ETA. I executed many different road tests and retained the data which I presented to Lexus for their analysis. As I said in my earlier post, they were unable to provide an answer or a solution to the problem. Based on the post by Don222, it appears that they have not corrected the issue in subsequent years.

mcomer

Have you set up Lexus App Suite (not LAS 2.0) in your paired phone yet? The native Lexus Navigation
knows where the fuel stations are, LAS knows how much the fuel costs. "Gas Buddy" apps are fine but you
are not supposted to be holding the phone while driving, right? The fuel cost feature of LAS sorts by location
or price and drops the destination right into the Navigation.

The other source of updated information that comes from keeping LAS running on your paired phone
is the Traffic (green, yellow and red "corridors") on the Map and the Weather Channel. Noticed you are
in Canada but down here you can keep "HD" Hybrid Digital AM and FM stations tuned in and get updates.
If you only listen to Satellite or Podcasts then you must rely on LAS to stay current.

I am not sure if LAS also updates the MPH we have been discussing but perhaps it would help.

Don222

I checked the trip to visit my granddaughter. 800 miles. Lexus nav used 58 mph as the average speed. Google maps used 65, and Apple used 68. All but 5 miles on interstate highways.

when I took the actual trip, the Lexus nav was grossly incorrect even at 60 miles from the destination.

the data base had the correct speed limits. The nav calculations are clearly wrong, at all times.

as I stated in my original post, I was very pleased with the old system. It hard to believe the level of incompetence at Lexus, to break a good system. I wonder what other programs are faulty in this vehicle.