Degree of separation from motor vehicles

Why is it important?

Sharing the carriageway with fast moving motor vehicles is both a safety hazard and discomfort. But segregation can also have negative consequences, creating conflicts with perpendicular traffic or pedestrians. Most cycle highways mix stretches of segregated cycle paths and carriageways shared with motor vehicles, with degree of separation best adapted to local context.

Minimum and recommended values

Acceptability of mixed traffic solutions, depending on motorised traffic speed and volume. The drawing is intentionally...

Guidelines and standards in different countries give different thresholds at what speed and volume of traffic separation of bicycles is recommended or necessary. As a rule of thumb, streets with 30 km/h speed can be considered safe for cyclists. But:

• Cycling between large number of cars, even if they drive slowly, might not be comfortable, and in some cases also slow down the cyclists. Bicycles are not meant to be stuck in a traffic jam! According to the Design Manual for Bicycle Traffic, cycling on carriageway feels natural up to 500 cars/day, and might be comfortable up to 2500 cars/day if the number of bicycles exceeds the number of cars.
• If cars are rare and there are not too many distractions around (e.g. outside built-up area), drivers have plenty of time to notice a cyclist and react, so limiting the speed to 30 km/h might not be high priority. In extreme case the reduced standard in Qualitätsstandards für Radschnellverbindungen accepts up to 800 cars/day and speed up to 70 km/h outside built-up areas.

Atypical for Netherlands double solution on Waterleidingstraat near Nuland – part of cycle highway F59 ‘s Hertogenbosch...

The decision to separate or not depends also on:

• available width of the corridor
• junction density
• volume of pedestrian traffic

One needs to assess whether it is realistic to provide enough space for segregated cycling paths, separation from pedestrians and good visibility splays on junctions. A cycling path, where a cyclist comes into a crossing from just behind a fence might not be safer than riding in mixed traffic on a carriageway. On the other hand, without separated cycle infrastructure on a busy street some cyclists might decide to use the sidewalk. Below is the summary of main considerations for the available choices.