3 ms·

My understanding is that these systems use a combination of posted sign identification and GPS data.

deleted 3y ago
[deleted]
Jtsummers 3y ago
Right. Here the databases are wrong so the GPS data will indicate 25mph and the sign looks like a speed limit sign so posted sign identification will likely be tripped up (again, based on reports from Tesla owner friends and colleagues). So for 1/4 of a mile on a 50mph road cars that automatically enforce the speed limit will be screwing up. And I doubt this is a unique situation.
- woodruffw 3y ago
  That sounds pretty unique to me; I've done a few 1000+ mile road trips across the US and have never run into a sign that looks like a speed limit but isn't actually one. The closest thing would be a yellow advisory sign, but those don't look like speed limits. (This sounds like the kind of thing you should report to either your state or county -- AFAIK every state maintains a DB of posted limits with geofences, and correcting them is generally a high priority for ticketing reasons.)
  - sokoloff 3y ago
    Loads of towns around Boston have the exact setup described above.
    - woodruffw 3y ago
      Do you have an example? Not that I don't believe you; it just seems nuts to me that any state would have a sign that looks almost exactly like a speed limit but that isn't one. For the record: I've gone through the length of MA a couple of times (NY to Boston), and have never noticed these. But maybe that's because I thought they were all speed limits.
      - sokoloff 3y ago
        For a road that I commuted on a lot: At the town line entering Lexington, MA, they have posted the default Lexington-wide speed limit: https://www.google.com/maps/@42.4098312,-71.2076201,3a,75y,302.01h,95.09t/data=!3m6!1e1!3m4!1sdIRJ47YR1x52rjvRWVMd5g!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4098312,-71.2076201,3a,75y,3... That road, Concord Ave, is posted as a 35 or 40 mph road for its length. (The MassDOT GIS database lists that first segment in Lexington as having a 40 mph speed limit, object_id = 395024.) At 94 (about 1500' ahead), Concord Ave is posted as 35 mph: https://www.google.com/maps/@42.4131439,-71.2130807,3a,75y,342.62h,69.35t/data=!3m6!1e1!3m4!1s128iHeMTthOuI1KD_6nIug!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4131439,-71.2130807,3a,75y,3... At 190, posted as 35: https://www.google.com/maps/@42.4156383,-71.2191302,3a,75y,316.66h,83.36t/data=!3m6!1e1!3m4!1s_b2KRm5cPIho3WEX4YWtBA!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4156383,-71.2191302,3a,75y,3... At 72 (in the other direction) posted as 40: https://www.google.com/maps/@42.4126782,-71.2123193,3a,75y,104.55h,74.53t/data=!3m6!1e1!3m4!1sRX62PX8wNan0PkpzYcrW5w!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4126782,-71.2123193,3a,75y,1... Mass Ave, entering Lexington: https://www.google.com/maps/@42.425451,-71.1924309,3a,75y,289.05h,110.92t/data=!3m6!1e1!3m4!1srvQa0ASJF78eDteOv8nvHg!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.425451,-71.1924309,3a,75y,28... Mass Ave shortly ahead, posted at 30: https://www.google.com/maps/@42.4277977,-71.2025678,3a,75y,266.5h,103.4t/data=!3m6!1e1!3m4!1s18K9rnJNDAQbkjcXOaqq-g!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4277977,-71.2025678,3a,75y,2... Rt 30, entering Newton: https://www.google.com/maps/@42.3398206,-71.1676001,3a,75y,220.92h,92.78t/data=!3m9!1e1!3m7!1sjspZIXOUroor8EOxwh1v7w!2e0!7i16384!8i8192!9m2!1b1!2i48?entry=ttu https://www.google.com/maps/@42.3398206,-71.1676001,3a,75y,2... 500-ish feet ahead: 30 mph: https://www.google.com/maps/@42.3394727,-71.1686319,3a,75y,220.92h,92.78t/data=!3m9!1e1!3m7!1siGP6UNTardoP-d-1xOvBBg!2e0!7i16384!8i8192!9m2!1b1!2i48?entry=ttu https://www.google.com/maps/@42.3394727,-71.1686319,3a,75y,2... I believe a casual sign-reader could easily see the default sign and mistakenly conclude the speed limit on the pavement they are on is 25 mph. If I was stopped for 30 in the vicinity of any of the default limit signs I posted, I really, really like my chances to have it dismissed.

deleted 3y ago

[deleted]

Right. Here the databases are wrong so the GPS data will indicate 25mph and the sign looks like a speed limit sign so posted sign identification will likely be tripped up (again, based on reports from Tesla owner friends and colleagues). So for 1/4 of a mile on a 50mph road cars that automatically enforce the speed limit will be screwing up. And I doubt this is a unique situation.

woodruffw 3y ago
That sounds pretty unique to me; I've done a few 1000+ mile road trips across the US and have never run into a sign that looks like a speed limit but isn't actually one. The closest thing would be a yellow advisory sign, but those don't look like speed limits. (This sounds like the kind of thing you should report to either your state or county -- AFAIK every state maintains a DB of posted limits with geofences, and correcting them is generally a high priority for ticketing reasons.)
- sokoloff 3y ago
  Loads of towns around Boston have the exact setup described above.
  - woodruffw 3y ago
    Do you have an example? Not that I don't believe you; it just seems nuts to me that any state would have a sign that looks almost exactly like a speed limit but that isn't one. For the record: I've gone through the length of MA a couple of times (NY to Boston), and have never noticed these. But maybe that's because I thought they were all speed limits.
    - sokoloff 3y ago
      For a road that I commuted on a lot: At the town line entering Lexington, MA, they have posted the default Lexington-wide speed limit: https://www.google.com/maps/@42.4098312,-71.2076201,3a,75y,302.01h,95.09t/data=!3m6!1e1!3m4!1sdIRJ47YR1x52rjvRWVMd5g!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4098312,-71.2076201,3a,75y,3... That road, Concord Ave, is posted as a 35 or 40 mph road for its length. (The MassDOT GIS database lists that first segment in Lexington as having a 40 mph speed limit, object_id = 395024.) At 94 (about 1500' ahead), Concord Ave is posted as 35 mph: https://www.google.com/maps/@42.4131439,-71.2130807,3a,75y,342.62h,69.35t/data=!3m6!1e1!3m4!1s128iHeMTthOuI1KD_6nIug!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4131439,-71.2130807,3a,75y,3... At 190, posted as 35: https://www.google.com/maps/@42.4156383,-71.2191302,3a,75y,316.66h,83.36t/data=!3m6!1e1!3m4!1s_b2KRm5cPIho3WEX4YWtBA!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4156383,-71.2191302,3a,75y,3... At 72 (in the other direction) posted as 40: https://www.google.com/maps/@42.4126782,-71.2123193,3a,75y,104.55h,74.53t/data=!3m6!1e1!3m4!1sRX62PX8wNan0PkpzYcrW5w!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4126782,-71.2123193,3a,75y,1... Mass Ave, entering Lexington: https://www.google.com/maps/@42.425451,-71.1924309,3a,75y,289.05h,110.92t/data=!3m6!1e1!3m4!1srvQa0ASJF78eDteOv8nvHg!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.425451,-71.1924309,3a,75y,28... Mass Ave shortly ahead, posted at 30: https://www.google.com/maps/@42.4277977,-71.2025678,3a,75y,266.5h,103.4t/data=!3m6!1e1!3m4!1s18K9rnJNDAQbkjcXOaqq-g!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@42.4277977,-71.2025678,3a,75y,2... Rt 30, entering Newton: https://www.google.com/maps/@42.3398206,-71.1676001,3a,75y,220.92h,92.78t/data=!3m9!1e1!3m7!1sjspZIXOUroor8EOxwh1v7w!2e0!7i16384!8i8192!9m2!1b1!2i48?entry=ttu https://www.google.com/maps/@42.3398206,-71.1676001,3a,75y,2... 500-ish feet ahead: 30 mph: https://www.google.com/maps/@42.3394727,-71.1686319,3a,75y,220.92h,92.78t/data=!3m9!1e1!3m7!1siGP6UNTardoP-d-1xOvBBg!2e0!7i16384!8i8192!9m2!1b1!2i48?entry=ttu https://www.google.com/maps/@42.3394727,-71.1686319,3a,75y,2... I believe a casual sign-reader could easily see the default sign and mistakenly conclude the speed limit on the pavement they are on is 25 mph. If I was stopped for 30 in the vicinity of any of the default limit signs I posted, I really, really like my chances to have it dismissed.