News:

Thanks to everyone for the feedback on what errors you encountered from the forum database changes made in Fall 2023. Let us know if you discover anymore.

Main Menu

VMS travel times displays that account for speeding

Started by briantroutman, July 20, 2017, 01:00:07 PM

Previous topic - Next topic

briantroutman

I routinely encounter a VMS that usually has travel times posted on it. And during low traffic periods with no congestion, the furthest junction is listed as 12 miles - 12 minutes. This caught my attention, though, because the entirety of that 12 miles is posted at 55, and so it would be impossible to legally drive the distance in 12 minutes. No matter how you round, it would take just over 13 minutes at the legal speed.

So I wondered: Do these travel times calculators typically have any provision to cap the time estimate at the maximum legal speed, or do they simply calculate their estimates based on the average speed regardless of how high it might be? Does anyone have examples of extreme cases–where the meeting the time estimate would require speeding by a significant margin?

On a semi-related topic, I've also wondered how speed limits play into ETA calculations on GPSes (if at all). On Apple Maps, I've noticed that if I drive anywhere near the speed limit (let's say 70 in a 65 zone), the ETA will gradually creep forward in time–indicating I'm not traveling as quickly as the app assumes I would be. I've noticed that I typically have to maintain 80+ on freeways just to keep the ETA stationary.


hotdogPi

Quote from: briantroutman on July 20, 2017, 01:00:07 PM
On a semi-related topic, I've also wondered how speed limits play into ETA calculations on GPSes (if at all). On Apple Maps, I've noticed that if I drive anywhere near the speed limit (let's say 70 in a 65 zone), the ETA will gradually creep forward in time–indicating I'm not traveling as quickly as the app assumes I would be. I've noticed that I typically have to maintain 80+ on freeways just to keep the ETA stationary.

Waze is the same.
Clinched, minus I-93 (I'm missing a few miles and my file is incorrect)

Traveled, plus US 13, 44, and 50, and several state routes

I will be in Burlington VT for the eclipse.

jeffandnicole

Quote from: briantroutman on July 20, 2017, 01:00:07 PM
I routinely encounter a VMS that usually has travel times posted on it. And during low traffic periods with no congestion, the furthest junction is listed as 12 miles - 12 minutes. This caught my attention, though, because the entirety of that 12 miles is posted at 55, and so it would be impossible to legally drive the distance in 12 minutes. No matter how you round, it would take just over 13 minutes at the legal speed.

So I wondered: Do these travel times calculators typically have any provision to cap the time estimate at the maximum legal speed, or do they simply calculate their estimates based on the average speed regardless of how high it might be? Does anyone have examples of extreme cases–where the meeting the time estimate would require speeding by a significant margin?

On a semi-related topic, I've also wondered how speed limits play into ETA calculations on GPSes (if at all). On Apple Maps, I've noticed that if I drive anywhere near the speed limit (let's say 70 in a 65 zone), the ETA will gradually creep forward in time–indicating I'm not traveling as quickly as the app assumes I would be. I've noticed that I typically have to maintain 80+ on freeways just to keep the ETA stationary.

Yeah, that's on 95 near Philly.  It's an odd one, as the ones before and after it don't account for such a speed (60 in a 55).

I think there was one in NJ which accounted for a higher speed than the limit.  Of course, there's always the one asshole out there that writes the newspaper complaining how the state apparently encourages speeding and since speed kills why is there a sign with a time faster that the limit.  The minimum time was changed to show it no faster than what the limit would allow.

I mentioned in another thread about construction VMSs in NJ (for the 295/42/76 project) that were posting average speeds.  On Rt. 42, a 55 mph highway, one sign kept showing 60 mph during free-flow conditions.  Yet, another one fully in a 65 mph zone never went higher than 55 mph.  They've all been since turned off.

SectorZ

Quote from: briantroutman on July 20, 2017, 01:00:07 PM
On a semi-related topic, I've also wondered how speed limits play into ETA calculations on GPSes (if at all). On Apple Maps, I've noticed that if I drive anywhere near the speed limit (let's say 70 in a 65 zone), the ETA will gradually creep forward in time–indicating I'm not traveling as quickly as the app assumes I would be. I've noticed that I typically have to maintain 80+ on freeways just to keep the ETA stationary.

An old Garmin GPS I had was obscene with how fast you needed to drive to keep up with the ETA. Portable TomTom I have now seems to expect a "just under speed limit" ride, and my Mazda's built-in GPS adds a ridiculous 10 minutes per hour to the time to get somewhere on most routes.

Pink Jazz

I know NMDOT in the Albuquerque area shows a range instead of an exact number of minutes.  I wonder if they are accounting for this.

Joe The Dragon

Quote from: jeffandnicole on July 20, 2017, 01:10:20 PM
Quote from: briantroutman on July 20, 2017, 01:00:07 PM
I routinely encounter a VMS that usually has travel times posted on it. And during low traffic periods with no congestion, the furthest junction is listed as 12 miles - 12 minutes. This caught my attention, though, because the entirety of that 12 miles is posted at 55, and so it would be impossible to legally drive the distance in 12 minutes. No matter how you round, it would take just over 13 minutes at the legal speed.

So I wondered: Do these travel times calculators typically have any provision to cap the time estimate at the maximum legal speed, or do they simply calculate their estimates based on the average speed regardless of how high it might be? Does anyone have examples of extreme cases–where the meeting the time estimate would require speeding by a significant margin?

On a semi-related topic, I've also wondered how speed limits play into ETA calculations on GPSes (if at all). On Apple Maps, I've noticed that if I drive anywhere near the speed limit (let's say 70 in a 65 zone), the ETA will gradually creep forward in time–indicating I'm not traveling as quickly as the app assumes I would be. I've noticed that I typically have to maintain 80+ on freeways just to keep the ETA stationary.

Yeah, that's on 95 near Philly.  It's an odd one, as the ones before and after it don't account for such a speed (60 in a 55).

I think there was one in NJ which accounted for a higher speed than the limit.  Of course, there's always the one asshole out there that writes the newspaper complaining how the state apparently encourages speeding and since speed kills why is there a sign with a time faster that the limit.  The minimum time was changed to show it no faster than what the limit would allow.

I mentioned in another thread about construction VMSs in NJ (for the 295/42/76 project) that were posting average speeds.  On Rt. 42, a 55 mph highway, one sign kept showing 60 mph during free-flow conditions.  Yet, another one fully in a 65 mph zone never went higher than 55 mph.  They've all been since turned off.
some should use that to fight the ticket in court if it listed an speed that is over the limit

cl94

Quote from: 1 on July 20, 2017, 01:10:12 PM
Quote from: briantroutman on July 20, 2017, 01:00:07 PM
On a semi-related topic, I've also wondered how speed limits play into ETA calculations on GPSes (if at all). On Apple Maps, I've noticed that if I drive anywhere near the speed limit (let's say 70 in a 65 zone), the ETA will gradually creep forward in time–indicating I'm not traveling as quickly as the app assumes I would be. I've noticed that I typically have to maintain 80+ on freeways just to keep the ETA stationary.

Waze is the same.

Waze does NOT use speed limits in its calculations and, in fact, it is the only navigation app that reliably accounts for the average travel speed of users on a road segment. If traffic generally moves 5 above, for example, Waze will calculate your ETA using that speed instead of the speed limit. In areas without speed data, 30 mph is generally assumed. If you're comfortable driving "with traffic" and you'll be spending most of your time in places with a lot of users, Waze will give the most reliable ETA of any navigation app.

Google Maps, on the other hand, bases ETA calculations on speed limits unless traffic speeds are slower.
Please note: All posts represent my personal opinions and do not represent those of my employer or any of its partner agencies.

Travel Mapping (updated weekly)

Duke87

Quote from: cl94 on July 20, 2017, 08:06:20 PM
Google Maps, on the other hand, bases ETA calculations on speed limits unless traffic speeds are slower.

I'm not sure what the hell Google does, all I know is it changed significantly at some point in 2014-2015. Used to be that the time Google gave you was extremely easy to beat, you had to drive like a total grandpa for it to take that long.

But in the past few years I've found that Google Maps pretty reliably underestimates how long it takes to get anywhere with the exception of relatively short mostly-freeway trips. On long trips they underestimate how long it takes because their times do not account for any necessary stops. Meanwhile on local streets (at least in New York City), it almost seems as though they are not counting any time you spend stopped at red lights in their estimates.
If you always take the same road, you will never see anything new.

cl94

Quote from: Duke87 on July 20, 2017, 08:46:07 PM
Quote from: cl94 on July 20, 2017, 08:06:20 PM
Google Maps, on the other hand, bases ETA calculations on speed limits unless traffic speeds are slower.

I'm not sure what the hell Google does, all I know is it changed significantly at some point in 2014-2015. Used to be that the time Google gave you was extremely easy to beat, you had to drive like a total grandpa for it to take that long.

But in the past few years I've found that Google Maps pretty reliably underestimates how long it takes to get anywhere with the exception of relatively short mostly-freeway trips. On long trips they underestimate how long it takes because their times do not account for any necessary stops. Meanwhile on local streets (at least in New York City), it almost seems as though they are not counting any time you spend stopped at red lights in their estimates.

And on surface roads in rural areas, it grossly overestimates, especially on minor roads. On my clinching trips, I would beat the time even with gas/restroom stops included, occasionally with meal stops.
Please note: All posts represent my personal opinions and do not represent those of my employer or any of its partner agencies.

Travel Mapping (updated weekly)

vdeane

Depends on the area.  I find that on upstate roads, it's about right (I generally keep to 5-7 mph of the speed limit, so this may not hold true if going faster).  It did seem to overestimate how long some of the pavement survey trips would take, though, particularly in Essex County.  Meanwhile, it underestimates how long trips predominantly in the Hudson Valley or southern New England take, sometimes vastly so.  My recent clinching trip along the southern part of the US 7 corridor took over an hour longer than I estimated from Google Maps (granted, I use the "without traffic" time, not whatever time it happens to report when I plot the route, and then add in a little extra for traffic/stops/stuff that's hard to plot on Google Maps, usually half an hour to an hour).  It also seems to underestimate how long things take in Pennsylvania for some reason, even on an all-freeway trip.
Please note: All comments here represent my own personal opinion and do not reflect the official position of NYSDOT or its affiliates.

briantroutman

#10
Of course it's hard to say for sure, given that both systems are essentially black boxes as far as the outside user is concerned, but I assume Google Maps and Apple Maps use similar methodologies to calculate ETAs since they usually give me estimates that are within about a percent of each other. I predominantly use Apple Maps since my car is compatible with CarPlay and displays Apple Maps information on the car's built-in touchscreen (Apple blocks third-party apps like Google Maps and Waze from doing so).

But regardless, I'm not so sure that either uses speed limits as a cap on estimated speed (and therefore ETA). Just as a simple "for instance" , I ran an estimate on I-180 in PA from just east of Exit 21 (PA 87) to I-80, and Google Maps estimates that as 20.8 miles and 18 minutes, which corresponds to 69.33 MPH–this despite the entirety of that stretch being posted at 65. Even if we go so far as to assume that the time estimate of "18 minutes"  has been rounded down from 18.9, that would still correlate to 66–not dramatically above the speed limit, but still higher.

For me, those most noticeable examples of this travel time underestimation come when I'm driving late at night on a nearly empty Interstate–weary from a long day and anticipating the moment I pull up to my freeway-side hotel for the evening. I'm maintaining 75 in a 65 zone, and yet  I see my ETA gradually slipping away–12:58 a.m., then 1:01, 1:04, and so on until I finally reach my hotel at 1:08 a.m.–I haven't stopped anywhere or encountered any traffic.

You could theorize that the ETA is adjusting outward because of a traffic tie-up that I have yet to encounter, but if it's cleared up before I get to that point (and in fact I don't encounter a slowdown), the ETA should eventually go back to its previous time, shouldn't it? The only other conclusion that I can reach is that the app assumes I should be going 80 or 85 in that 65 zone–instead of 75. At 1 a.m. on a rural Interstate, there isn't much of a "prevailing rate of traffic"  per se. So perhaps if very few people are using Apple Maps at that hour–and those that are, are driving 20+ above the speed limit, that would throw of the average speed...and therefore the ETA.

Joe The Dragon

Quote from: briantroutman on July 20, 2017, 09:58:07 PM
Of course it's hard to say for sure, given that both systems are essentially black boxes as far as the outside user is concerned, but I assume Google Maps and Apple Maps use similar methodologies to calculate ETAs since they usually give me estimates that are within about a percent of each other. I predominantly use Apple Maps since my car is compatible with CarPlay and displays Apple Maps information on the car's built-in touchscreen (Apple blocks third-party apps like Google Maps and Waze from doing so).

But regardless, I'm not so sure that either uses speed limits as a cap on estimated speed (and therefore ETA). Just as a simple "for instance" , I ran an estimate on I-180 in PA from just east of Exit 21 (PA 87) to I-80, and Google Maps estimates that as 20.8 miles and 18 minutes, which corresponds to 69.33 MPH–this despite the entirety of that stretch being posted at 65. Even if go so far as to assume that the time estimate of "18 minutes"  has been rounded down from 18.9, that would still correlate to 66–not dramatically above the speed limit, but still higher.

For me, those most noticeable examples of this travel time underestimation come when I'm driving late at night on a nearly empty Interstate–weary from a long day and anticipating the moment the I pull up to my freeway-side hotel for the evening. I'm maintaining 75 in a 65 zone, and yet  I see my ETA gradually slipping away–12:58 a.m., then 1:01, 1:04, and so on until I finally reach my hotel at 1:08 a.m.–I haven't stopped anywhere or encountered any traffic.

You could theorize that the ETA is adjusting outward because of a traffic tie-up that I have yet to encounter, but if it's cleared up before I get to that point (and in fact I don't encounter a slowdown), the ETA should eventually go back to its previous time, shouldn't it? The only other conclusion that I can reach is that the app assumes I should be going 80 or 85 in that 65 zone–instead of 75. At 1 a.m. on a rural Interstate, there isn't much of a "prevailing rate of traffic"  per se. So perhaps if very few people are using Apple Maps at that hour–and those that are, are driving 20+ above the speed limit, that would throw of the average speed...and therefore the ETA.

do they have a min speed level they default to when there is little live data to feed the sensors

epzik8

From the land of red, white, yellow and black.
____________________________

My clinched highways: http://tm.teresco.org/user/?u=epzik8
My clinched counties: http://mob-rule.com/user-gifs/USA/epzik8.gif

02 Park Ave

I thought that their data was based upon actual E-ZPass monitoring.
C-o-H

roadman

Quote from: 02 Park Ave on July 21, 2017, 12:59:00 PM
I thought that their data was based upon actual E-ZPass monitoring.
Travel time systems are not based on E-ZPass monitoring, but detection of Bluetooth devices.
"And ninety-five is the route you were on.  It was not the speed limit sign."  - Jim Croce (from Speedball Tucker)

"My life has been a tapestry
Of years of roads and highway signs" (with apologies to Carole King and Tom Rush)

Rothman

Quote from: roadman on July 21, 2017, 01:12:34 PM
Quote from: 02 Park Ave on July 21, 2017, 12:59:00 PM
I thought that their data was based upon actual E-ZPass monitoring.
Travel time systems are not based on E-ZPass monitoring, but detection of Bluetooth devices.
TRANSCOM was definitely using E-ZPass data for travel time data.  Whether it feeds VMSes, I am uncertain.

*personal opinion expressed*
Please note: All comments here represent my own personal opinion and do not reflect the official position(s) of NYSDOT.

jeffandnicole

There are several methods to determine travel times.  I know NJDOT uses a combination of EZ Pass, Bluetooth and something else to determine their travel times.

SectorZ

Quote from: Rothman on July 21, 2017, 03:07:38 PM
Quote from: roadman on July 21, 2017, 01:12:34 PM
Quote from: 02 Park Ave on July 21, 2017, 12:59:00 PM
I thought that their data was based upon actual E-ZPass monitoring.
Travel time systems are not based on E-ZPass monitoring, but detection of Bluetooth devices.
TRANSCOM was definitely using E-ZPass data for travel time data.  Whether it feeds VMSes, I am uncertain.

*personal opinion expressed*

Massachusetts uses bluetooth in this state, so maybe it varies from state to state. Bluetooth is certainly newer technology than E-ZPass.

noelbotevera

This happens usually late at night in my case.

There are VMSes on I-81 at the PA/MD state line and around MM 40 and MM 41, to my knowledge. If it was around midnight to 2 AM, the VMSes display these:

(PA/MD line)
US 11 52 MILES 47 MINUTES
I-78  89 MILES 84 MINUTES 


(MM 40)
US 30 24 MILES 20 MINUTES
PA/MD LINE 40 MILES 37 MINUTES



Opinions expressed here on belong solely to the poster and do not represent or reflect the opinions or beliefs of AARoads, its creators and/or associates.