Last updated 22-9-2013
In many cases a road has several numbers. This is also known as a multiplex. Under which conditions is this possible? This depends on the country, road classes in question (in particular whether both numbers have the same class), the road type (like motorway, expressway or ordinary road) and rules can have exceptions for example depending on TOTSO's. In Europe, the following rules of thumb hold:
Note that in practice, E roads are never concurrent with lower road classes like Kreisstrassen in Germany or C roads in France and Great Britain.
There are exceptions, in some cases a national road is concurrent with a motorway for a short distance and is indicated on signs.
Usually the lowest number applies, but there are exceptions to this, for example if the road with the higher number is older, or it continues straight on while the other road in question has TOTSO's.
In the tables below, the diagonal refers to numbers of the same class. The upper right half applies to road signs while the other half is about the administrative aspect. In the small squares, the upper right corner applies to the class in the top row, and the lower left corner to the class in the left column.
1 = indicated
0 = not indicated
km = only visible on kilometerage or mileage signs
All = all numbers are used or indicated
Lowest = only the lowest of several numbers are indicated
n.a. = not applicable: the classes in question never occur close together or no road of one class is ever numbered in such a way that it could continue across a road of the other class.
Example:
In this country, there are two road classes A and B. If a road has several A numbers, they area all signposted and also used in administration. When a road has several B numbers, only the lowest is used for administration, and only that one is indicated, but only on km signs.
If a road has both an A and a B number, only the A number is indicated on signs, but only the B number is used for administration.
Note: if the same rules apply to administration and signs, then the matrix is symmetrical.
* A numbers usually only appear on km signs on motorways with E numbers. However, on roads whose E number was assigned in 1995 and which previously only had an E number, the A number sometimes appears on directional signs. On the A54/E420 only an A number appears, on the A8/E429 and A17/E403 the A number is sometimes signposted.
In exceptional cases, an A road does not have motorway standard, and then also has an N number.
The R43a was replaced by B404 but both numbers are visible on some signs.
T roads almost never appear on signs, and when they do, only on km signs like T302. Many of these roads are not even accessible to motorised traffic.
As administrative lists like 'Rodovias Estaduais Coincidentes' on the DAER Rio Grande do Sul site showed, several numbers can follow the same route also for administrative purposes. However, in many states, state highways only appear on km signs, and such signs always only have one number.
There are currently no R roads that run via D roads, but such a situation will exist when the D11 is completed around Hradec Kralove and the R35 is extended towards Liberec.
The only case where two R roads have the same route is the R35 and R46 on the Ololouc ring road.
When a national road is concurrent with a R road, it is indicated in the same way as the R road so one could argue it is also an R road on that section, but this is not done from an administrative point of view.
* For D and M numbers, higher numbers can be more important than lower numbers, because downgraded N numbers often receive a high 3-digit or even 4-digit number. For example, in Grasse, the D6085 is much more important than the D11.
* The A46 shares the A57 between Kreuz Neuss-West and Dreieck Neuss-Süd. This was originally the A57, and the A46 has TOTSO's at both interchanges. Therefore the kilometerage continues only on the A57 and the A46 is less well signposted.
* Exceptions are possible, for example State Highways 5 and 18 in Andhra Pradesh are concurrent for a few km east of Kalwakurthy, and because SH18 continues straight on, this is indicated on signs. However, note that there are only km signs.
No National Expressways with an Asian Highway number are known so far, but it may be assumed that new National Expressways will carry Asian Highwys. The only know example of an Asian Highway without (new) national number is the AH2 between Bamanpuri (NH9) and the border with Nepal. This is probably a State Highway.
Whether National Expressways can also have National Highways is unknown, especially with the new grid system. As can be seen on the schematic map, roads can have several numbers (indicated in black for the main routes).
Note: N numbers over 400, though of a higher class than s and r numbers, are rarely signposted and usually only appear on km signs, while s and r numbers are generally indicated.
Road numbers are generally very poorly signposted in Russia, but in principle several numbers can be indicated, see e.g. panoramio 51765562.
N (H) numbers are for administration only and are probably never assigned together with other numbers.
There is only one instance of two concurrent AP roads: the AP-2 and AP-7. On km signs, only AP-7 is indicated.
Autovías can be national (e.g. A-1) but also be subordinate to a Community (e.g. A-92) or a province (most urban expressways). In the table above, for Autovía read the expressway specific numbers in blue and red (see the 'Autovía' and 'Other (local) main road' columns in Road number colours Spain).
The class Carretera Comarcal (C) is left out because this class is obsolete and these numbers have almost all disappeared.
There are several sub classes of community and provincial roads. When several are concurrent, the most important one takes precedence.
Motorway numbers (A) were introduced in 1996 mostly for motorists. For administration, often the (old) National highway number is used.
Some N numbers still appear on directional signs, but only on indirect references in cities. On many old km signs, the N numbers still appear, but most signs either show the A number instead or no number at all.
Hauptstrassen numbers are a national administrative system, of which only the 1- and 2-digit numbers are also meant for motorists, though some cantons never (Genève, Basel-Stadt, Nidwalden) or rarely (Valais, Ticino) show them on signs.
Most cantons also have a cantonal numbering system, which is for administration only, and sometimes encompasses the national systems of National highways and Hauptstrassen. In a more and more cantons these numbers now appear on white km signs, mostly like this, but Thurgau and Uri have their own models.
* Primary A routes are preferred over secondary routes. Primary routes can have higher numbers. For example, in Stow-on-the-Wold, the A424 and A429 follow the same route, but the A429 is primary and the A424 secondary. Only the A429 appears on signs.
The Ipswich bypass is the A12 and A14, and the A14 is only slightly more important. The A12 is indicated between brackets. This may also have to do with the fact that the A14 continues without TOTSO's.
The case of the A40 and B4009 (between Oxford and High Wycombe) shows that TOTSO's play a role: the A40 has two TOTSO's while the B4009 continues straight on. On advance directional signs both junctions are combined onto on sign in each direction, and the continuing roads are all indicated, but at the junction, only the B4009 is indicated on the multiplex section.
In many cases, when two roads follow the same route, the less preferred number is indicated between brackets. This also applies to A roads via Motorways and B via A roads.
In principle all numbers are indicated on signs, but Secondary state and County highways tend to be signposted less well than other roads, depending on the state.
In some states (Florida and Georgia), all Interstate and U.S. highways also have a State highway number.
Marcel Monterie