Somehow the "r" got cut off the end of my handle. It should be kudzurunner.
I actually joined Club Lexus forums because of what I'll call the "lousy nav system" issue, one that I discovered for myself yesterday and then was delighted (or depressed) to discover is a significant issue among Lex owners.
My 2013 RX 350 is one week old and I love the heck out of it. But the nav system, with factory settings, is obviously non-optimal. Yesterday it told me that the 55 mile trip from Tupelo to Oxford, MS would take 1:36, when anybody knows that it only takes an hour. (Google maps has 60 minutes; my Garmin nuvi has 57 minutes.)
I've used the Garmin for the past three years with great success when I go off on long-weekend or two week roadtrips. I'm a part-time musician and having accurate distances and ETA's is absolutely critical to making a tour function smoothly. So this is a huge issue, and it freaked me out.
A little research made clear two things:
1) I needed to adjust the three speed settings in the setup preferences
2) Lexus, which is ahead of the curve in every other way, seriously lags behind Garmin and others in the matter of navigation technology--at least when accurate ETA's are concerned. Garmin, as I understand it, knows the speed limit on every piece of road on your planned route, so the ETA is calculated from that. (As a result, it also lets you know, in real time, when you're exceeding the posted speed limit--a really useful thing when limits suddenly change and cops are waiting just across that pesky Iowa state line.) Lexus doesn't.
I was gratified to discover the handful of threads devoted to this issue. But I was also determined to see whether I could optimize my Lexnav in a way that would give me basic confidence in its ability to shepherd me through a tour.
What I did was come up with a list of 11 destinations, from 55 to 1150 miles away. These are places I've actually driven to. First I mapped them with Google maps to get distance and ETA (or, more precisely, TTD--time to destination) data. I did the same thing with my Garmin. This gave me a reasonable baseline: a pretty accurate register of the true distance and TTD.
Then I ran those destinations through the Lexnav five times, beginning with the OEM mph settings (25, 35, 65) for in-town, regional, and highway speeds respectively. The other four settings were:
1) 25, 45, 70
2) 25, 50, 65
3) 25, 50, 70
4) 25, 55, 70
The results were fascinating--and heartening.
First, at least when mapping trips that begin where I live (Oxford, MS), the OEM settings lead to atrociously inaccurate results. This has something to do with Interstate speed limits around here (and in Tennessee) being 70, but that single fact doesn't explain all of the problem. The 35 mph middle setting is also way too low.
Second, although no single set of settings is perfect, the last two (25, 50, 70 and 25, 55, 70) are surprisingly accurate. On an 1150 mile trip to suburban New York, the 25/50/70 setting gets me there within 5 minutes of the Google/Garmin estimate--in a trip lasting more than 17 hours!
Thirdly, a musician pounding down the highway towards the next gig would always prefer to be slightly ahead of time rather than slightly late, which means if I have a choice, I'd always prefer a nav system that tells me that my TTD is slightly longer than it actually is. That being the case, setting #3 (25, 50, 70) works best for me--which is to say, it comes closest to equalling the average of Google maps and a Garmin. This is especially true at longer distances. At shorter distances (under 100 miles), the top setting (25, 55, 70) seems to be slightly more accurate. (These results surely have something to do with the direction I'm traveling on the longest trip, which is East. Highway speed limits fall from 70 to 65, for the most part, as you head east and as I-40 gives way to I-81 (except in W. Va.)
Fourth, the Lexnav generally came up with a trip distance that was very, or reasonably, close to the distance given by Google/Garmin, but on several occasions there were significant anomalies. The trip from Oxford MS to Mankato MN was almost 70 miles and an hour longer in Lexnav than in Google/Garmin. So no matter how well one optimizes the Lex, it's probably a good idea, at least with long trips where the ETA is crucial, to use Google maps as a backup.
I have put all the results into an Excel spreadsheet and uploaded it to Tradebit, a filehosting site that I've used for six years. If you'd like to download it for free, you can do so by accessing the following link:
There's a lot more to be done here, but the basic principle seems sound to me. When confronted with a non-optimal system--which the Lexnav plainly is, as any Garmin owner will attest--don't assume the worst. Engage in retail optimization. Plug in a lot of data, adjust what is capable of being adjusted, and optimize the non-optimal system in an incremental way. Then reassess.
If you don't have a Garmin and don't want to spend a couple of hundred bucks just to optimize your Lexnav, then just use Google maps. It'll give you a pretty good baseline. Choose at least 5-7 different destinations--different directions, different types of roads, different trip-lengths--and come up with distance and TTD data. Then run those same trips through your Lexnav, tweaking the three speed settings until most of the trips hew fairly close to the Google results.
What this experiment has shown me is that I'm likely to bring my Garmin along on working roadtrips and start the morning by running BOTH the Garmin and the Lexnav, just to see whether they're in reasonable agreement. If they are, I'll turn off and stow the Garmin. If they're not, I'll try to figure out why they're not; I may tweak the Lexnav speed settings and see if that helps.
Cheers, everybody! I love the heck out of my new car--my first new car, at age 54, after a lifetime of used Hondas. Big step up!