How are the US interstate highways numbered?

Interstate Route Numbering Major Interstate routes are designated by one- or two-digit numbers. Routes with odd numbers run north and south, while even numbered run east and west. For north-south routes, the lowest numbers begin in the west, while the lowest numbered east-west routes are in the south.

Why are interstates numbered?

The number of digits tells you whether an interstate connects multiple metro areas, or exists solely within a single metro area. One and two-digit interstates span multiple regions, while three-digit interstates are more local. The rest of the system flows from this most basic starting point.

Why do some interstates have 3 numbers?

When an interstate hits a major urban area, beltways around the city carry a three-digit number. These routes are designated with the number of the main route and an even-numbered prefix. To prevent duplication within a state, prefixes go up.

How are California freeways numbered?

Each highway is assigned a Route (officially State Highway Route) number in the Streets and Highways Code (Sections 300-635). Most of these are numbered in a statewide system, and are known as State Route X (abbreviated SR X). United States Numbered Highways are labeled US X, and Interstate Highways are Interstate X.

How did freeways get their numbers?

The California Department of Transportation picks the numbers. I asked how this was done and was pointed to a Web site. It was created by road fan Daniel P. Faigin, who explains that two-digit routes usually have odd numbers if they run north or south and even numbers if they run east or west.

How many interstate highways are in California?

12
California | 12 active routes | 2,457.34 mi. Colorado | 5 active routes | 951.85 mi.

What do the numbers on the Interstate Highway System mean?

Generally, north/south highways have odd numbers that get higher from east to west, while east/west ones have even numbers that get higher from north to south. Major routes mostly end in 1s and 0s while three-digit numbers tend to represent secondary or spur highways. Map of the Interstate Highway System

How many miles are in the US interstate system?

The interstate system totals 46,300 miles. All interstate highways are marked by blue signs with red tops. The north-south highways have odd numbers with 1 or 2 digits, usually including a 5. The lowest numbers are on the West Coast and increase as they move east.

What is the difference between one-digit and two-digit Interstates?

One and two-digit interstates span multiple regions, while three-digit interstates are more local. The rest of the system flows from this most basic starting point. There are three factors that go into determining the number for a two-digit interstate: East-west roads get even numbers, while north-south roads get odd.

What is an example of an odd numbered highway?

All routes which go generally north-south are odd-numbered. One example is Interstate 35 which goes from Loredo, Texas to Duluth, Minnesota. All routes which go generally east-west are even-numbered. Interstate 90 goes from Boston to Seattle.