I hereby present with you the USA national guidelines for mapping Speed Limits. There are some sections purposefully left up to local decisions, please check your local guidance for these in your local wikis.
Namely;
Just saw a question in WME chat
The final sentence in the first paragraph “These are marked with black lettering on white rectangular signs”. The editor’s question was whether to map speed limits where there are no signs at all, but where the law clearly states speed limits for these areas.
Are most editors going to be able to figure out that this sentence was meant to apply to places with signs, and not to places without speed limit signs? That they need to find and follow local guidance for roads where no speed limit signs are posted?
Or do we need to make a slight change to avoid confusion?
Finally. Only requested this page how long ago? 
Looks great. Guess I’ll update my original post to link to this for US editors.
Sent from my Galaxy Tab A using Tapatalk
I made a section in my draft local page to emphasize that Maryland is a state where statute sets the speed limit, and signs are only to modify those limits. I don’t know how this would carry to other states.
So how would one driving on Maryland roads know what the speed limit is if there are no signs? I could have sworn it was a federal regulation (FHWA MUTCD) that stated SL signs are to be placed every XXX feet/miles based on the speed.
Not to get in the weeds, but maryland has three speed limit statutes:
Talking to my cop friends, if you are driving on a road, and haven’t yet seen a speed limit sign, they can still ticket you, take you to court and win based on rule #2. Plus, rule #1 always applies.
EDIT: Ignorance of a law is not excuse, apparently for #2.
EDIT 2: Here’s the quote I’m looking for, MUTCD (both federal and MD) defines a statutory speed limit:
As mentioned above this is defined in state law and must be handled in state wiki. I’ve started the NY wiki section with the statutory statewide SL for NYS and NYC.
Typically these “Area speed limits” as defined in the MUTCD are also posted on all major roads into the area, and at jurisdictional borders on black and white regulation signs, and state the area they apply to.
Sent from Android using Tapatalk
No the MUTCD merely states that speed limit signs indicating statutory speed limits shall be installed at entrances to the State and, where appropriate, at jurisdictional boundaries in urban areas. But I wouldn’t call that a federal regulation.
If I may be allowed to ask for one clarification in addition do what voludu2 posted above:
For locations where the speed limits change at an intersection per a local municipality ordinance, how should we map speed limits when the change of the speed limit occurs within an intersection with a divided road?
Example:
Where B, is the middle/center segment that has crossed divided road, and where A has the speed limit of 45, C has the speed limit as 50, as defined by the local city ordinance. What speed limi properties should segment B be labeled?
From what I am reading in the Wiki,
As most of these center segments are under 100 feet therefore it would not really be appropriate to cut those segments in two and I agree with that.
While it could just be blank, should it be treated like AGC’s (if I am understanding the SL rules to AGC’s) and therefore would have use the SL of the segment feeding into it, so therefore B would have the SL of 45 going to C, and then have a SL of 50 going to A (also applying to the divided road’s two one central one way segments)?
The rule I have seen requiring a speed limit sign to be posted every X number of feet is only for a linear speed limits which are different than the area speed limit. So for example if a state has a speed limit of 55 miles an hour and a specific road has a different speed limit for that road of 65 miles an hour or 45 miles an hour then on that road it would require a speed limit sign every X number of feet to indicate that it is different than the state speed limit. I know this is definitely true for New York State and if it’s different in other States, each state can handle this in their state wiki.
Agreed, as far as I can tell Maryland just requires “appropriate signs giving notice of the limit.”
The goal here, when you are not creating a new junction, is to have the speed limit change at the junction closest to where new limit actually goes into effect. Therefore in a state where speed limits change at the sign, and the sign is posted after the intersection, the new speed limit should only be applied to the segment which is after the intersection. The junction closest to where the change is effected is the junction between B&C in your >ABC> example. Meaning The median segment (B in your example) would still carry the old speed limit.
However in a state where the change is effective at the intersection, then as soon as you enter the intersection the new speed limit is in effect. Therefore in such a state the median should carry the new speed limit since you are already in the intersection when you get on the median segments.
Example segment A is posted as 30, (segment B has no signs,) segment C is listed as 50:
State law SL change at sign;
↓ ↑
→ A 30 | B 30 | C 50 →
← A 30 | B 50 | C 50 ←
↓ ↑
State law SL change at the intersection;
↓ ↑
→ A 30 | B 50 | C 50 →
← A 30 | B 30 | C 50 ←
↓ ↑
All state-managed roads in NJ have their speed regulations described in very nice detail right down to exact speed zones and exact locations of their boundaries in the state DOT website. For those roads, it’s definitely a more reliable source than hunting down speed limit signs in SV, which may or may not be there depending on how the road’s zone’s SL compares to the state’s default SLs.
But the speed limits different from the statutory speed limits are not enforceable unless there are signs. Such a speed limit “shall be prima facie lawful at all time or at such time as may be determined, when appropriate signs giving notice thereof are erected at such intersection, or other place or part of the highway.” NJ Statutes 39:4-98. But yes there need be no signs for the statutory speed limits.
I wouldn’t want the USA guidelines to get into any particular detail about the various state guidelines.
The only change I would suggest is to make clear that we are not limiting ourselves to speed limits only in cases where there are signs.
Issues about the speed limit on median segments in states where the speed limit begins at an intersection but the sign comes up to 200’ after should be handled in the states’ own wiki pages.
I would also suggest a minor edit in the section #Fixed regulatory speed limits
from: added to the road corresponding segments in the WME.
to: added to the corresponding road segments in WME.
I think this is an important point, as in Massachusetts the state laws explicitly defines speed limits when not posted, going into so much detail as to describe the density of the houses to distance of road for a certain speed limit. There no reason when laws like that exist that we cant get the entire state
I do think we should add a small section defining the two methods for choosing a median segment SL which I mentioned just above. The state wikis can stipulate which method to use.
Sent from Android using Tapatalk
Several editors have been asking what the guidance should be for adding (or not) speed limits to roundabouts.
In my opinion Roundabouts should be treated very similarly to ramps.
If there is a posted SL on the RA, it should be used. If the SL before and after the RA are all identical, then that should be used. If there is no posted SL, and there are different SLs depending on approach or exit, then the RA should be left blank.
I’d like to add a section to the SL wiki for the USA for roundabouts to follow the same rules as ramps.
There are 2 benefits here.
Any comments or critiques and objections, or to agree and show support please post below.
There have also been no comments on adding the median segment guidance mentioned above, and reposted last Friday. If there are no objections I will add that section as well. Please comment below to show your support or concern.
I agree with this completely.
I see no problems with this guidance either. I presume that each state would need to define which method they’re using on their state wiki?
Can anyone find an RA with a posted SL? I highly doubt the speed limits on a RA match the connecting segments. You would normally be at a slower speed since traffic coming into an RA has to slowdown or yield to other traffic.
I also don’t think that not mapping Ra’s will have that big of an effect on the overall score. It’s not like every intersection is an RA.
Sent from my Galaxy Tab A using Tapatalk