What is the traffic volume cut off between high-volume and low volume?
The question is not something with an absolute answer as there is more than just traffic volume involved in the answer. The number of trucks and functional classification of the highway also need to be reviewed. From chapter 2 in our Basics of a Good Road workshop manual, here are simple definitions of the various functional classifications.
- Principal arterials
major interstate systems, and major federal and state highways, linking states and major population centers.
- Minor arterials
less traveled state and county highways linking smaller cities and major towns.
- Rural collectors
both major and minor collectors that typically serve regional intra-county travel. They link the smaller population centers with the rural areas.
- Local roads
connecting businesses and farms to the smaller communities and individual homes. They are mainly used by local residents in the course of their normal business.
- Very low-volume roads
local roads with an average daily traffic of fewer than 400 vehicles per day.
Here are a few points that are worth nothing.
- The 400 vehicles per day split between very-low volume and low-volume is basically a line where the number of vehicles in the busiest hour of the day is about 1 vehicle per minute. A lower design standard can be applied for such highways as almost all of the traffic is local drivers. The standard on the Cornell Local Roads Program website utilize this traffic value. For higher volume highways, agencies should use something like the NYDSOT Highway Design Manual unless they have their own standards
- 1,000 vehicles per day is a typical cut off for low-volume to high-volume, but there are ranges for this value that can be quite different. This value can range from around 500 to near 2,000 depending upon context including functional classification.
Classifying a highway is not always easy as many roads and streets serve both as a local road where people live and a collector that brings traffic to the arterials. In fact, some people live on arterials. Here is a link to the functional classification maps that show what NYSDOT and FHWA have designated for various highways around the state.