[Talk-us] Speed Limit Validity in US Questions

[Paul Johnson]

On Fri, Jul 2, 2021 at 9:21 AM Horea Meleg <horea.meleg at telenav.com> wrote:

> Hello all,
>
> I'm Horea Meleg and I'm part of the Map Analyst Team at Telenav.
>
> We have some questions regarding speed limits, and your input will be
> really helpful, because we don't want to wrongly map this feature:
>
> 1. A speed limit sign is valid until next intersection, or until next
> speed limit sign encountered?
>

I'm going to speak very generally to the broadest commonality since each
state varies slightly.  It varies by context.  Normally when you pass the
sign the new speed applies, but if it's right after an intersection, it's
from the preceding intersection, with a grey area from that intersection to
the sign.  Speed limits often change at an intersection and due to spatial
constraints, it's not possible (or at least wildly impractical) to just
plunk a sign down in the middle of the intersection.  Consider 15th and
Lewis in Tulsa where Lewis goes from 25 MPH to 35 MPH at the intersection
southbound, and from 35 to 25 northbound.


> 2. If it's until next intersection, which is considered as intersection?
> Any kind of highway type? Or there are some special rules?
>
> For example:
>
>    1.    T intersection it’s considered?
>    2.    Cross intersection it’s considered?
>
> These are both intersections as far as the law cares.

3.  Speed Limits marked on the road are considered as valid, or just those
> posted on a traffic sign? Meaning it could be added the information in OSM
> based on speed limit road markings?
>

Signs on the ground count the same as signs on the pole, but markings
outside the core MUTCD vary *substantially* by state; you may need to check
the MUTCD supplement for the state you're looking at to be sure if you're
not familiar with that area.
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