Contraflow cycling means that cyclists are allowed to ride in both directions on a street that is one-way for cars.
The idea stems from the observations that:
a street might be too narrow for two cars to pass each other, but still wide enough for a car and a bicycle;
one-way streets often serve to filter out through traffic from residential areas (see filtered permeability); while it is necessary to protect local streets from through motorised traffic, cycling does not generate noise or pollution.
Traffic calming – especially in connection with alternating the direction available for cars, to remove through traffic, as a form of filtered permeability.
Contraflow cycling can be implemented by cycle path(s), cycle lane(s) or just by road signs in mixed traffic without any form of segregation. The usual recommendations for a necessary degree of separation from motorised traffic apply, and if separation is applied, the cycle path or lane needs to meet the relevant requirements.
In the further part of the section we focus on contraflow cycling on carriageways with no dedicated space for cyclists. Two discussion points are recurring in discussions regarding the solution: width of the carriageway and priority (or lack of it) on intersections.
Insufficient width is sometimes considered a safety hazard, making some decision-makers reluctant to authorise contraflow on narrow streets. The Dutch “Design Manual for bicycle traffic” recommends a width of carriageway of between 3.50 m and 4.85 m, depending on the traffic volume and location, but other countries with lower levels of cycling traffic have reported positive experiences with legalising contraflow cycling also on narrower roads:
In Brussels 43% of streets with contraflow authorised have less than 3.5 m width and no negative impact on safety has been identified (see case study below).
A Hungarian study found out that on narrow one-way streets cyclists feel relatively more comfortable cycling against the traffic (2.8 on a scale from 1 to 5, source: “How Many Hungarians Cycle?”), than with it (2.0 in the same survey).
Relatively higher levels of both objective and perceived safety can be linked to better mutual visibility when passing a car driving in opposite direction than when being overtaken by one driving in the same direction.
Contraflow cycling is mostly applied on lower class, lower speed streets. In many countries these streets usually do not have assigned priority on intersections. No-priority intersections are even considered as one of area traffic calming measures. But if a street with contraflow cycling forms a part of cycle highway, following the priority-to-the-right rule on each junction can significantly increase the number of interruptions. Therefore, if a street with contraflow cycling is to become a cycle highway, it should have priority over other streets that play a less important role in the bicycle network. No-priority junctions should be replaced with other traffic calming measures. Note that streets with contraflow cycling can also be bicycle streets.
The Brussels Capital Region authorised contraflow cycling over a relatively short period on 404 km of one-way streets. The impact on road safety was evaluated in-depth by the Belgian Road Safety Institute.
Contraflow cycling 
