[Talk-us] Speed limit editing in Detroit

Paul Johnson baloo at ursamundi.org
Sat May 6 08:07:25 UTC 2017

On Fri, May 5, 2017 at 7:55 AM, Horea Meleg <horea.meleg at telenav.com> wrote:

> Hello all,,
> Me and my Telenav colleagues are planning to start editing speed limit in
> Detroit area and we found the following situation:
>    1. There’s a trunk road which continues with a motorway but we don’t
>    have a speed limit sign at the beginning of the motorway. Do you think we
>    should add the speed limit value from position 1 or 2 on the highlighted
>    segment?
> 42.4985931, -83.3042949 à Position 1 (50 mph)
> 42.4941433, -83.2950564 à Position 2 (70 mph)
Assuming 1 and 2 are the points where there are speed limits, the speed
limit from point 1 would continue until the new sign at point 2.

>    1. A lot of motorway_links don’t have a speed limit sign. Do you have
>    any idea where could we get the speed limit values from?
> In North America, ramps with speed limits are relatively rare, but
following the usual rule that the previous speed limit applies, the speed
limit of the off-ramp would be the same as the freeway itself unless
otherwise posted, and if the same ramp returns to the freeway contiguously,
that speed limit would continue to carry over to the on-ramp.  It's not
very much more complicated than that, but in practice, just leave off
maxspeed on the ramps entirely unless it's actually posted with a
regulatory (white sign) speed limit or a general speed limit is known (both
relatively uncommon). maxspeed:advisory would be far more common, as exit
ramps are nearly universally posted with an advised (yellow sign) speed.
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