A diversion is a measure of traffic control to enable or to make the traffic easier. If an existing traffic route cannot accommodate the expected or actual traffic, a detour must be set up. On the other hand, a derivation is set up for traffic routes that are blocked; there is no further traffic routing here.
In the case of railways, a diversion can take place through other line routes or rail replacement services .
In inland waterway transport, there are usually no diversion options, except through the rare interaction of networked rivers and canals . Also in hydraulic engineering , it may order draining a construction site to divert traffic route through the diversion tunnels come; in Weilburg an der Lahn there is the only German water tunnel for the purpose of diverting (paddle) boats past a barrage .
In air traffic , diversions to an alternate airport may occur; the airline must ensure transport to the original destination airport by other means of transport or other modes of transport as vicarious agents. In the case of streets, a diversion must be indicated by appropriate signs .
A diversion on demand is a special diversion for motorways, which is indicated by the sign No. 460 of the StVO .
Demand diversions are always used when a motorway is closed or a traffic jam occurs due to an accident or overcrowding. In general, routes at risk of congestion are relieved by need diversions.
Extract from the StVO :
- "The symbol  indicates an alternative route in the downstream road network between motorway junctions."
The administrative regulation for the StVO can be found in:
- For motorway traffic in the north or east, the diversions are to be designated with odd numbers and for motorway traffic in the south or west with even numbers. The numbers should be chosen so that they increase in the direction of travel. Numbers 1 to 99 are available for each country. The federal states ensure sensible coordination.
However, there are some exceptions to the rule: In Saxony-Anhalt the older motorways (e.g. the A 2 and A 9) are numbered continuously. In Saxony, the numbering for the even numbers is in descending order. There are also numbers greater than 99 in the Hamburg area.
If the diverted traffic cannot yet be diverted back to the motorway at the junction provided according to sign 460, this sign (466) will forward it via the next required diversion.
The diversion is ordered by the road traffic authority . Road users are guided to the corresponding streets by the road signs. The corresponding signs are directional signs: non-observance does not constitute a violation. The traffic routing is confusing for the road user if several diversions of various construction measures overlap. There are special planning groups in large cities to coordinate the construction work and thus the necessary diversions.
The residents affected by the construction site must be accessible as far as possible without using the diversion. In particular, the concerns of garbage disposal, the fire brigade and the bus routes must be observed.
The diversion should be planned in connection with the preparation of the planned disruption ( construction sites , folk festivals , etc.). Particular attention must be paid to the performance of the diversion route.
Long-term diversions can cause damage to the road, which the building contractor of the blocked route then has to bear. Likewise, modifications to signal systems or special traffic regulations ( one-way streets or cancellation of parking spaces ) are often necessary.
Redirection arrows are used to redirect traffic in the event of traffic jams or slow-moving traffic to parallel freeway routes that are usually less traveled. The prerequisite for this is a regionally sufficiently dense motorway network. This is the case, for example, in the Rhine-Ruhr metropolitan region , where the diversion arrow can be found in large numbers. There are also some deflection arrows in the Rhine-Main area and in some areas of the Saarland .