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 are forms of auxiliary routes.

Canada

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).

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 the number of the "parent" Interstate; e.g. a spur route of Interstate 90 would be 490, a spur route of Interstate 5 would be 805.

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 are also found branching from 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.

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.

ee also

* Loop route