Monday, August 12, 2013

Access Points for residential subdivisions

City codes typically mandate a certain width of road--typically enough for two travel lanes and on-street parking on both sides of the street. Developers like to minimize the amount of road per subdivision. Which makes sense. Grass is cheap, asphalt is expensive. They also like to minimize 'through' traffic, and so the development plats tend to have a single exit per subdivision. Which is great if you live in that particular subdivision, but hell on walkability. It's also hell on the performance of external streets--instead of some of the 'local' traffic taking places on these local streets, it all gets dumped onto high speed arterials...disrupting traffic flow, and slowing traffic. Which is problematic, as arterial streets are much much more expensive to build that local streets. And, if the traffic volumes coming out of a residential subdivision are high enough, may make it necessary to have a traffic light, at additional cost to the city, and impairment to the function of the road. Western Hills Drive, in South Jordan, is a fine example of such, with over 200 houses, and only one access point.

Adding more access points in a residential subdivision means fewer cars turning in an out of a subdivision, as use of the access is divided over more points. It also means that residents get off arterial streets faster, as they can take the more direct route to their homes, rather than needing to circle the block first. Quality city planning also mandates that developers include 'stub' streets. Streets that do not (as of yet) connect to anything, but that will connect whatever gets built in the next parcel over. Wondering if it might not be possible to go one further, and add a calculation such that there must be 1 'access point' for every 10 acres, or for every 70 units. (Or some similar ratio).