4 + 0 traffic routing - 4+0-Verkehrsführung
In road construction, 4 + 0 traffic routing is understood to be a construction-related transfer of directional traffic from two to one directional lane in the area of a job . The prerequisite for this is a suitable road cross-section that is both sufficiently wide and adequately paved.
By using the 4 + 0 traffic routing, one lane becomes traffic-free, so that construction work can be carried out there with almost no disruption. The method thus represents an alternative to building under the rolling wheel . On the other lane, the traffic flows are separated from one another and guided by means of construction site markings , marking buttons and passive protective devices .
Due to this traffic routing, one-way traffic has a limited lane width. Therefore, a speed limit and an overtaking ban for trucks are imposed there. The left-hand lane is usually only so wide that it can only be used by cars and motorcycles. In order to avoid accidents in the future, signs are being set up as an experiment, prompting people to move around. 
Despite numerous safety measures, traffic accidents often occur in such sections . The reasons for this, in addition to the limited space, are often excessive driving speeds and unclear traffic management. The latter applies particularly at the beginning and at the end of the assignment (so-called transfer or return).
Particularly critical situations can arise in the event of a vehicle breakdown when using the hard shoulder (4s + 0 traffic routing), as the broken-down vehicle cannot be removed from the road immediately and the following traffic is significantly hindered.
The guidelines for the construction of streets - cross-section result in a width of 11.50 m for two-lane motorways with two lanes plus hard shoulder. The lanes have a width of 3.75 m each, the hard shoulder 2.50 m plus marked edge strips of at least 0.50 m (or 0.75 m). In a 4-0 system, this RQ 29 (or RQ 29.5) is redistributed into 3.00 m (or 3.25 m) for the truck lanes and 2.50 m for the car lanes 0.15 m to 0.25 m wide strips for the markings.
Norms and standards
- RVS 05.05.40 ff. - Construction site protection
- SN 640 885c - Signalization of construction sites on motorways and motorways