Speed limits affect the safety of people walking. Let’s think about the way we talk about speed limits, because this affects the conversations that we have about safety.

Many people who drive are skeptical about changes to speed limits for cars. They have understandable concerns about what speed limits mean for travel time. Travel time is often viewed as dead time to be minimised (although it is worth noting that this is true only of cars, not other forms of transport), and in many situations, travel time is increasing as traffic increases.

Now, in most cases travel time is increasing precisely because average speed is decreasing (often below 20kmh in peak periods). Problematically, where this is the case, drivers seeking “reliability” are anchored to their average journey time and therefore compare losses in congestion to potential gains on free moving sections, at speed.

Consider what someone who drives each day might think about a proposed change to a street in their neighbourhood, when the following three phrases are used:

• lower speed limit
• safer speed limit
• safe speed limit

The first phrase, lower speed limit, brings a simple consequence to mind for the driver: driving will take longer. This is frustrating, particularly when driving in traffic is already a stressful task (is there are losses incurred which cannot be regained). The understandable reaction is therefore to oppose the change.

The second phrase, safer speed limit, introduces a different concept. Can we improve the safety of people on the road? Maybe things are fairly safe already, but they could be a bit safer? How much safer? Is it worth the inconvenience of taking longer to drive somewhere?

Finally, the third phrase is safe speed limit. This directs the conversation to a yes or no question: do we want speeds that are safe, or speeds that are unsafe? And then: Can we agree that safe means no-one is seriously injured or dies? It is harder to argue for speeds that are unsafe. This conversation can then be directed to finding out which speed limits are safe, and perhaps even to the research on how many people are injured or die when certain speed limits are imposed. It can also link to ambitions like Vision Zero, where no-one on any street has to die or be seriously injured.

One last tweak. If we discuss speed limits that are safe for everyone we can extend the conversation beyond just those in cars (drivers and passengers) to other road users, such as those walking and cycling. These other road users don’t always come to mind for drivers discussing regulations that affect car use.

Further tweaks are also available around the speed you are anchoring to – is there a lower average speed, average peak speed or are there any other conditions that might slow cars like corners and school zones? In these cases, seek to anchor to the existing lower speed, say by positioning the move as matching the speed limit to actual speeds, or improving safety for everyone by lowering late night speeding // speeding around corners etc.

Last, consider the context for the change. Is this an overall streetscape improvement or better local centre, of which the safe speed forms just one element of an otherwise good news story for everyone.

What phrase will you use next time you write or talk about speed limits? What phrase does your council use?