Spur route

A spur route is a short road forming a branch from a longer, more important route (typically a major road, freeway, Interstate Highway or motorway). A bypass or beltway is never considered a true spur route as it typically reconnects with the major road. Both loops and spurs can be forms of special route.

In Ontario

See also: 400-series highways (Ontario)

In the province of Ontario, most spur routes are designated as A or B, such as Highway 17A, or 7B. A stands for "Alternate Route", and usually links a highway to a town's central core or main attraction, while B stands for "Business Route" or "Bypass", but are used when a main highway is routed around a town and away from its former alignment. The designation of "C" was used twice (Highway 3C, and 40C), and is assumed to mean "Connector". Both highways have long since been retired and are now county roads. There was also one road with the D designation (Highway 8D, later the original Highway 102), and this may have stood for "Diversion", as it was along the first completed divided highway in Canada at the time (Cootes Drive in Hamilton).

In the United States of America

In the United States, a good deal of the Interstate Highway System bypasses cities and towns. For example, the metropolis of Pittsburgh, Penn. does not have any one- or two-digit Interstate Highways passing though it. Instead, it has sever Interstate Highway spur routes which connect it with Interstate 70, Interstate 76, and Interstate 79. Another example is Huntsville, Alabama, which has the spur route Interstate 565 that connects it with Interstate 65.

Thus, a good number of Interstate Highways have spur routes which connect them with certain metropolitan areas. Furthermore, even within some metropolitan areas where the major Interstate Highway passes through them, there are spurs connecting it with other parts of the city. Examples of this include Interstate 395 in Baltimore, even though Interstate 95 itself passes through Baltimore, and Interstate 105 in Los Angeles, even though Interstate 5 passes through Los Angeles.

All Interstate Highway spur routes are numbered with three-digit numbers, with their first digit being an odd number. The last two digits of the number are the number of the "parent" Interstate; e.g. a several spur routes of Interstate 10 are Interstate 110. For the single-digit Interstate Highway 5, a zero in incorporated into its a spur route number, such as Interstate 105, Interstate 305, and Interstate 505. (In the case of the only other single-digit Interstate Highways in the Contiguous United States, Interstate 4 and Interstate 8, this rule has not come into play because they do not have any spur highways.)

[Incidentally, all of the Interstate Highway bypass routes are also numbered with three-digit numbers, but with their first digit being an even number. Examples of these include Interstate 285, Interstate 495, Interstate 640, and Interstate 805].

It is also allowable to have Interstate Highway spur route that branch off of Interstate Highway bypass routes. Examples of these include I - 795, which branches off I - 695 near Baltimore, and I - 795 never connects directly with I - 95 at all.

Spur Interstate routes have three-digit numbers with an odd first digit. Any subsidiary route either going through a city (while the main route bypasses it) or bypassing a city, perhaps looking all the way around it as a beltway - for example Interstate 275 - and then reconnecting with the major Interstate Highway receives an even first digit. A good example of a bypass Interstate Highway that does NOT form a loop route is Interstate 495 which goes around three sides of Boston - where the fourth side is the Atlantic Ocean.

There are several numbering violations in this scheme of numbering the spur routes and the bypass routhes, hence the general rules described above are not ironclad.

Interstate Highways that have all five possiblities of numbered spur routes include Interstate 90, which has I-190, I-390, I-590, I-790, and I-990. Also, there is not a rule that commands these spur routes to have consecutive numbers. For example, Interstate 85 has I-185, I-385, and I-585, and I-985, but no I-785.

United Kingdom

In the UK, a spur route carries the same definition, but the rules for numbering it differ.

Same-number spurs

Short spurs from primary roads or motorways typically are not given a unique number, and three arms of the junction will apparently have the same number. For example, the A14 has a same-number spur to the A1(M) motorway at Huntingdon in Cambridgeshire, the M23 motorway has one to Gatwick Airport in West Sussex and the M25 has one to Heathrow Airport. To distinguish the spur on road signs, the road it leads to is usually given - for example "Gatwick Airport (A23)".

Unique-number spurs

Typically, slightly longer spurs, or those with intermediate junctions of their own, are given unique numbers to distinguish them from their parent road. There is a loose numbering system for these spurs on the motorway network, not dissimilar to the US system – the road takes a three-digit number derived from that of the parent road. Examples include the M602 motorway (spur of the M60 and M62 motorways), M621 motorway (spur of the M62 and M1 motorways), and M271 motorway (spur of the M27 motorway). There are anomalous spur numbers though, for instance the M898 motorway (spur of the M8 motorway; number given to match with a unique A-number road) and the unique case of the M181 motorway, a spur of a spur.

A-road spurs do not follow a noticeable numbering system; they would be impossible to assign due to the quantity of A-road numbers in use.

India

The Indian National Highway system designates spur routes of the main National Highways with alphabets. For example, National Highway 1 has 4 spur routes: NH 1A, NH 1B, NH 1C and NH 1D, the shortest of which is just 6 km in distance (NH 1C) and the longest is 663 km (NH 1A). While the spur routes essentially originate at the parent National Highway, they are not essentially secondary in status as some of the spur routes serve important cities in India (Srinagar, the capital of the state of Jammu and Kashmir is served by the spur route NH 1A). Some spur routes are specifically used to connect important Indian ports. (e.g. NH 5A links Paradip with its parent NH 5, NH 7A links Tuticorin with NH 7).

See also

• Special route
• Loop route