Spur route
From Wikipedia, the free encyclopedia
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 spur route as it typically reconnects with the major road.
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[edit] United States
In the US, many Interstate Highways have spur routes when they enter a large metropolitan area. Interstate spur routes are numbered with a three-digit number. The last two digits of the number are is the number of the "parent" Interstate; e.g. a spur route of Interstate 90 would be x90, a spur route of Interstate 5 would be x05.
Spur Interstate routes have three digit numbers with an odd first digit, while a subsidiary route either passing through a city or bypassing it would receive an even first digit. For example, in the case of Interstate 5's spur routes in Los Angeles, Interstate 405 goes through the entire city, whereas Interstate 105 ends at Los Angeles International Airport.
Spurs can be branches off of other highway types, too (US highways, state routes, etc.), often as extended onramps and offramps of expressways.
There are many numbering violations in the spur route numbering system, thus the general rules above do not always apply.
[edit] United Kingdom
In the UK, a spur route carries the same definition, but the rules for numbering it differ.
[edit] 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, and the M23 motorway has one to Gatwick Airport in West Sussex. To distinguish the spur on road signs, the road it leads to is usually given - for example "Gatwick Airport (A23)".
[edit] 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 dissimiliar 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.
