Indiana State Road Numbering System


The Indiana state road numbering scheme is fairly simple. Basically, odd-numbered highways go north and south and even-numbered ones go east and west. Lower numbers are on the east and north sides and higher numbers are are on the west and south. In other words, it is very similar to the US Highway numbering scheme.

In addition, three digit routes exist. Most run parallel to their parent route, but a few are perpendicular. For example, SR 134, SR 140, SR 520, SR 524, and SR 650 run the opposite direction to their parents. The ones where the cardinal direction is perpendicular from the parent are usually short spurs. Some are branches off their parent. For example SR 104, SR 105, SR 115, SR 167, SR 352 and SR 930 are children of SR 4, SR 5, SR 15, SR 67, US 52, and US 30 respectively. Others never touch their "parent". For example, SR 103, SR 117, SR 128, SR 213, and SR 236 run parallel to, but never meet their respective parents: SR 3, SR 17, SR 28, SR 13, and US 36. These are the most common. Yet other 3 digit route follow old routings of their parent. Examples are SR 158, SR 340, and SR 431. And yet another variant are the state road "placeholders" for future interstate designations. For example SR 265 and SR 469. Finally, some are children of parent routes that no longer exist. For instance, SR 129, SR 229, and SR 143 are children of routes that have been truncated, and SR 121, SR 234 and SR 135 are examples of children of routes that do not even exist anymore.

There generally are no state roads and US highways that share the same number. Until recently, US 131 and SR 131 existed on opposite sides of the state, however. SR 131 has been decommissioned since.

There are a few unexplainable anomolies. As a byproduct of this numbering scheme, several discontinuous sections exist. For example, there are two unconnected sections of SR 1, three unconnected sections of SR 114, and four unconnected sections of SR 101. If the numbering were random, discontinuous routes would not make sense.

An interesting phenomena of the numbering is how several US highways fit or almost fit into the state numbering system. Such examples are US 6, US 31, US 36, US 40, US 41, and US 50. In summary, it is a very straight forward and logical system.

Issues

In addition to the anomolies listed that still apply these issues exist that detract from the fundamental logic of the numbering system.
Recommended Numbering Changes

Realizing that any route changes are highly unlikely and as a fun exercise, here are some suggestions for numbering improvements anyway. Some are easier to accomplish than others:

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