3/5 Sustainable Safety principle – Predictability

In June 2014 we adopted Sustainable Safety as our first policy. Here we will describe the five principles of Sustainable Safety. This article will talk about Predictability and what it means.

We have previously discussed Functionality and Homogeneity. We explained the need for clear classification of roads and how the difference in speed and mass of vehicles creates a need for different types of cycle provision depending on the function of the road.

In Advancing Sustainable Safety by SWOV (http://www.swov.nl/rapport/DMDV/Advancing_Sustainable_Safety.pdf page 13) Predictability is described: “road environment and road user behaviour that support road user expectations through consistency and continuity in road design”.

Predictability is important to road users as predictable roads and users helps avoid confusion and with this the associated risk of errors is reduced.

Designing with care

In both the Netherlands and the UK a lot of the design documents are just guidelines rather than standards that must be adhered to. The difference in the Netherlands is the importance that Sustainable Safety plays in these guidelines and as part of this the need for nationally recognised designs that are predictable, which means that designs rarely stray far from the guidelines.

Below we are giving a few examples of measures that the Dutch have to provide a predictable road environment.

Surfacing

In the Netherlands it is becoming increasing common for cycle infrastructure to have a red surface, this is making it more obvious where cycles go and where people can expect cyclist to be.

A cycle path in Amsterdam, also the pedestrian pavement also has a different surface to help make it more predictable where pedestrians will be.

An photograph of a cycle lane from the CROW Design Manual for Bicycle Traffic

And a Cycle Street in ‘s-Hertogenbosch (courtesy of Bicycle Dutch)

In comparison the UK has many different colours that are still being used for cycle spaces.

Speed-setting design

The Dutch design roads and streets using techniques that suggest the correct speed to drive at. For a local street where speeds should be low, it is becoming common for streets to be designed with a surface that makes people feel they should drive slower.

In the image below a brick surface has been used along with a narrow carriageway design with street furniture also helping to increase the feeling of it being narrow. This street is also one way to motor traffic, the angles of the road at junctions helps to set people’s expectations of which way traffic should move, and makes it difficult to do anything different but to drive slowly.

 

Crossing a Cycle Lane

When crossing a cycle lane in a motor vehicle to enter or exit a side road, you would normally encounter something similar to the following. The cycle path colour continues through the junction and the road marking make it clear that cycles and pedestrians have priority. The consistency of giving cyclists and pedestrians priority at side roads ensures that people learn what to expect at a side road.

 

Summary

The key ideas that the Dutch have implemented through Sustainable Safety is that roads can be made predictable by using designs that set peoples expectations about how the road should be used and by following design guidelines as closely as possible so that the infrastructure provided becomes a standard that people become used to anywhere in the Netherlands.

Predicable road design allows people to safely assume what should be happening around them, and helps them to use the road in a way that others will find predictable. This makes it easier for all road users to navigate their environment and makes the journey less stressful. For vulnerable road users like pedestrians and cyclists the predictable road environment makes it less likely that error will occur that puts their safety at risk.