Interstate Highway

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Interstates have signs like this one to tell people which road they are on.

The Dwight D. Eisenhower National System of Interstate and Defense Highways (often called the Interstate Highway System, Interstate or I-), is a group of roads in the United States. They are grade separated, which means drivers must use a specially made group of ramps, called an interchange or exit, in order to get on or off the Interstate. Because of this, people are allowed to go very fast, sometimes up to 80 miles per hour (130 km/hr).

[change] Numbering

Interstates have a special way to figure out their numbers. Interstates that run east/west are even numbers, and north/south Interstates are odd numbers

[change] Three-digit interstates

Some cities have short freeways that get a three-digit number. That means that there is an extra number put behind the number of the Interstate. This number is even (2, 4, 6 or 8) if the Interstate goes around a city and connects with another Interstate, and odd (1, 3, 5, 7, or 9) if an Interstate goes into a city and ends at a street light. Numbers can be used again in different states. Three-digit Interstates usually go to the Interstate in their last two numbers. For example, Interstate 195 goes to Interstate 95.

[change] Examples

• Interstate 195 in Virginia goes into Richmond.
• Interstate 195 in New Jersey goes to eastern New Jersey.
• Interstate 275 in Florida goes around Tampa.
• Interstate 275 in Michigan goes around Detroit

Main Interstates (numbers ending in 0 or 5 in pink)
4	5	8	10	12	15	16	17	19	20	22	24	25	26	27	29	30
35	37	39	40	43	44	45	49	55	57	59	64	65	66	68	69
70	71	72	73	74	75	76 (W)		76 (E)		77	78	79	80	81	82
83	84 (W)		84 (E)		85	86 (W)		86 (E)		87	88 (W)		88 (E)		89	90
91	93	94	95	96	97	99	(238)		H-1		H-2		H-3
Unsigned			A-1		A-2		A-3		A-4		PRI-1		PRI-2		PRI-3

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