The Institute of Transportation Engineers published a recommended practice this year titled Neighborhood Street Design Guidelines. It’s a very good reference for anyone involved with the design of new neighborhoods. Table 1 shows recommended design elements derived from the report based on the density of the neighborhood.
In Minnesota, the statutory speed limit on local streets is 30 mph. Following are other design guidelines based on this speed (note the recommended practice also provides guidelines for other speed limits):
- Minimum stopping sight distance = 200 feet
- Minimum centerline horizontal curve radius = 300 feet
- Maximum grade in rolling terrain = 8% (2% at intersections)
- Clear sight distance provided at intersections without traffic control = 140 feet
- Corner radius at intersecting streets at 90 degree angle = 15 feet
- Minimum distance between tee intersections = 125 feet
The recommended practice provides discussion related to each of these design elements as well as other topics such as planning connectivity, utilities, street lights, parking, etc. The 64 page document is a handy reference for those working on neighborhood design and I highly recommend it.
One topic not covered in detail is when and what signs to use in neighborhoods. Given the budget pressures faced by agencies and research about the effectiveness of signs, I encourage you to minimize the use of all signs in new neighborhoods other than street name signs.