Star.pngStar.pngStar.pngStar grey.pngStar grey.png

Multiplex

From Roader's Digest: The SABRE Wiki
Jump to navigation Jump to search
Multiplex
A40-A449 Multiplex.JPG
On a few occasions road signs show the two routes in a multiplex as equal partners
Cameraicon.png Pictures related to Multiplex
View gallery (13)

Multiplex is unofficial terminology created by SABRE for a section of road where two numbered routes meet, share the same piece of road for a distance then go their separate ways again.

Terminology

The term is much used on SABRE but is not in general use by professional road engineers or administrators. Normally it is officially the case that each section of road has only one number, and the existence of a multiplex in a particular location is more of an inference rather than an indisputable fact. Indeed, some people reject the entire concept of a multiplex, though it does make sense to think of a multiplex as belonging to both routes that use it and some multiplexes are signed as such. Also, the 1935 Road numbering revision recognises the concept of a multiplex, though it uses the term merger to describe it.

In North America, the term concurrency is used, though not in all areas; whilst in parts of Australia such as Victoria, the term is combined route.

In the UK, Highways England Interim Advice Note 145/16 introduced the term braided route for such situations.

Multiplexes are often used in areas where geography proves challenging. Mid-Wales, for instance, has a large number of three-arm junctions, where in flatter terrain there might have been crossroads; so that the A470, the main north-south route through Wales, has multiplexes with the A40, A44, A489, A487 and (very briefly) the A483 and A5.

They are also commonly used in city or town centres, especially where the construction of a Ring Road has caused roads in the city or town centre to be downgraded. An example is the A1309 in Cambridge, where inside the city's ring road other routes take precedence.

Multiplexes in 1922 were rare

Signage

Sometimes multiplexes are indicated on signs that show distances to destinations with a pair of numbers where the recessive road number is bracketed.

There is no hard and fast rule or convention for signposting multiplexes though there are occasions where the roads in a multiplex have been signed as equal partners, that is to say, with two road numbers separated by a slash. Examples of this include the A40 and A449 in Monmouthshire and Herefordshire; and the A6 and A591 south of Kendal.

On some occasions, on signs indicating distances to major destinations en route, two multiplexed road numbers are shown in a pair where the "dominant" road number comes first and the "recessive" number is shown in brackets after it. Examples of this convention being used include the A10 and A1122 east of Downham Market and the A5 and A483 between Shrewsbury and Wrexham. Usually at junctions and roundabouts, the recessive number is shown in brackets by default as an indirect route to a destination, such as can be seen east of Ely where the A10 and A142 share a short section of road between two roundabouts.

Most frequently, however, road signs and maps only use the dominant number in a multiplex. This is particularly the case for shorter multiplexes where it is easy for drivers to make the connection between two sections of road that exclusively belong to a particular number.

Rarely, a multiplex may run in only one direction. An example is between the former B1507 and B1512 in the centre of Downham Market. This is due to the town's one way systems meaning the B1512 ran southwards along the B1507, but not northwards.

Frequency of multiplexes on UK and Irish Roads

A sign on a section of the A5 also belonging to the A483.

In the original 1922 road numbering scheme, multiplexes (or discontinuous routes) were avoided whenever possible, though some short lengths were created, including the A74 and A702 in Lanarkshire and Stanley Street (A6 and A59) in Preston. Now, there are numerous multiplexes up and down the United Kingdom. Notable examples include the A1(M) and A66 between Scotch Corner and Darlington; M60 northwest of Manchester (with M62 being the junior partner); the M9 and M876 near Falkirk; and the M6 Toll and M42 to the northeast of Birmingham. The last three of these are the only examples of a multiplex between two motorways.

In the Republic of Ireland renumbering of the network since the 1970s has resulted in only a very few instances of this phenomenon: those involving National roads / Motorways include the N13 and N14 near Letterkenny, the M6 and N52 between Mullingar and Tullamore, and the N11 and N31 (now a 'useless multiplex') to the south of Dublin / west of Dún Laoghaire.

'Useless multiplexes'

A so-called 'useless multiplex' (list) is a special type of multiplex where the dominant signed route in the multiplex ends, and the recessive road continues on. The name is often wrong, as actually they are useful - used where a major route would otherwise end on a more minor one not far from another major road. The classic example given is that of the A303 and A30 between Andover and Basingstoke, where heading eastbound the dominant A303 simply terminates at the M3 junction, and the recessive A30 continues eastwards.

Main Article: List of Useless Multiplexes

Links




Multiplex
Related Pictures
View gallery (13)
Multiplex - Coppermine - 12418.jpgA30-A33 - Coppermine - 12417.jpgGoodbye - Coppermine - 12416.jpgA40-A449 Multiplex.JPGA70-a721-carnwarth.jpg
Road Basics
Physical layoutSingle track • Single carriageway • Dual carriageway • High Quality Dual Carriageway • Road Widths • Urban Streets • Abandoned Road
Legal typesAll-purpose Road • Special Road • Motorway • Trunk road • Principal road • Classified Numbered road • Classified Unnumbered Road • Unclassified road • Primary Route • Non Primary Route • Right of Way • Unadopted road
Road numbers1922 Road Lists • Classification • Defunct road • Euroroutes • MoT Maps • National Cycle Network • Numbering principles • Numbering anomalies • Disputed Numbers • Recycled number • Unallocated numbers • Fictional Road Numbers • Junction numbers • Essential Traffic Routes
Road FeaturesArterial Road • Automatic Bollard • Balancing Pond • Belisha Beacon • Bott's Dots • Bypass • Cannon • Cats' Eyes • Cattle Grid • CD Lanes • Central Reservation • Chopsticks • Crash Barrier • Cuttings and Embankments • Cycle Lane • Emergency Phone • Escape lane • Expressway • Fingerpost • Flare • Ford • Gore • Green Bridge • Green Wave • Hairpin bend • Hard shoulder • Island • Junction • Layby • Level Crossing • Local Access Road • Managed Motorways • Milestone • Multi Lane Drop • Multiplex • No-Car Lane • Nose • Oxbow Road • Parapet • Petrol station • Play Street • Raised Pavement Markers • Ramp Metering • Retaining Wall • Road Studs • Roadside Art • Roadside Quarry • Roadworks • Secret motorway • Signage • Smart Motorway • Snow pole • Speed Limit • Spur • Street Lighting • Surface Dressing • Temporary terminus • Throughpass • Tidal Flow • Tiger tail • Toll booth • Traffic cone • Traffic Signals • Tunnel • Vehicle Recovery • Walking and Cycling Friendly Road • Weaving • Wig-Wag Signals • Winter Maintenance • Zip merge
Traffic CalmingBuild-Outs • Chicane • Dragon's Teeth • Home Zone • Low Traffic Neighbourhood • Pinch Point • Quiet Lane • Rumble strips • Safety Cameras • Sleeping Policeman • Speed bump
Public Transport FeaturesBus Lane • Bus stop • Guided Busway • Park and Ride • Tramway • Trolleybus System
Other termsAnderson report • Guildford Rules • Highway Authority • Highway Code • Model Traffic Area • Motorway alphabet • Pre-Worboys • Primary Destinations • Roads by 10 • Transport alphabet • Worboys report
AcronymsAADT • ADS • ANPR • ATM • DfT • GSJ • HA • HATO • HE • HETO • HQDC • LAR • LILO • LTN • MOVA • NCN • NMU • NRA • PBU • POPE • PTS • PFI • RCS • SABRE • SCOOT • SSD • SON • SOX • SRN • TEN-T • TERN • TfL • TII • TOTSO • TRO • TSM • TSRGD • UTC • VAS • VMS • VSL

SABRE - The Society for All British and Irish Road Enthusiasts
Discuss - Digest - Discover - Help