I'm building a street network dataset and want to adjust the speed limit of certain segments to account for road surface (paved vs. unpaved).

Are there any guidelines/rules for doing this (e.g. an unpaved road should be set to 5mph)?

closed as unclear what you're asking by Chris W, underdark Jun 30 '14 at 7:29

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    Are you asking what the rules should be or how to implement them? If what, then no, you get to make the rules or perhaps find some (I've been on unpaved comfortable at 60mph and paved I wouldn't go more than 5mph on), and this question would be off-topic. If you want how, that's another matter and could be done in a couple of ways. – Chris W Jun 18 '14 at 21:10
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    If you actually state which country you are working in, may be some expert for that country can give you an answer? – Hornbydd Jun 18 '14 at 22:53
  • I'm asking what the rules should be and I'm working in Worcester County, MA. – ZNR Jun 23 '14 at 15:13
  • To avoid your Question being put on hold I recommend that you edit it to make this clear and to address any other clarifications that may arise from potential answerers. – PolyGeo Jun 25 '14 at 23:07

To my knowledge there are no specific rules or guidelines for setting a speed limit based solely on surface type. Road geometry and access points are generally more important factors. Surface type might be a more heavily weighted factor in some cases, such as if dust is a concern in a residential area, but I've never seen a case where a specific speed limit was determined on surface type alone. I can think of numerous local (to me) examples of limit ranges on unpaved roads anywhere from 5mph to 50mph - even in the same governing body jurisdiction.

There are a couple of studies I found in a quick search regarding both what to set the speed limit at on an unpaved road and the effectiveness of doing so:

You might also contact the local county streets/traffic department where you are working.

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