ITO World provides an interactive map of speed limits for a growing but incomplete list of specific roads. Though no truly comprehensive alternative exists as of 2015, other resources are available to help keep motorists informed of speed limit laws and specific limits in some regions.
Sources such as the Governors Highway Safety Association and the National Motorists Association provide state-by-state speed limit laws for state-controlled roads and highways. They list not only the specific speed limits of these roads but also provide a good rule of thumb where more exact information is unavailable. Some regional authorities, such as the city of Sacramento, also offer more complete and detailed maps and databases of the specific speed limits in their areas.