A question about speed limit data on roads with no posted speed limits

I’ve been mapping out various towns/cities near where I live, and I came up with a question. There’s been hundreds of roads with absolutely no posted speed limit signs, but with speed limits defined in the city’s laws. The majority of these roads are highly urban residential roads, which have almost universally been defined as 25MPH zones in the laws, but, again, don’t actually have posted speed limit signs.

Would it be appropriate to add this speed limit data to OpenStreetMap? The alternative would be to just leave it blank, so it’s my impression that it’s a good idea to add it, but I thought it would be worth checking the general conventions.

It’s best to include the source of the speed limit but there are some caveats:

( https://wiki.openstreetmap.org/wiki/Key:source )
Perhaps the maxspeed:type should also be included for clarity.

Please also check this page about mass imports: https://wiki.openstreetmap.org/wiki/Import/Guidelines