More cyclists on the roads is associated with fewer fatal crashes. The safety in numbers effect might be part of the explanation but there are others that are arguably more important

This chart from Statista (see exhibit) shows how fatalities from cycling vary inversely with the level of cycling; fewer cyclists die (per kilometre) in countries with higher rates of cycling (km per capita). Statista suggests it’s due to the “safety in numbers” effect:

In an environment where bicycles and the infrastructure to support them are plentiful, awareness will be high. By contrast, a lone cyclist in a traffic choked urban environment is far more likely to end up in an accident, due to motorists who may not be aware/used to his or her presence.

Some caution is needed in interpreting the numbers in the chart. Reliable comparative data, especially kilometres of cycling, is hard to come by on a country-by-country basis. Also, this is a very small sample of countries and it’s highly selective; it’s likely the relationship would be much less marked given a substantially larger number of countries (or better still, cities). Note it also measures fatalities, not injuries; the former are relatively few in absolute terms e.g. 185 in the Netherlands (and 32 in Australia) in 2015.

But if we accept there’s probably some sort of inverse relationship between these variables, I doubt the explanation is as straightforward as Statista contends. Here are some hypotheses that might explain it:

Infrastructure. Places with high levels of cycling also tend to have a high standard of cycling infrastructure that segregates cyclists from collisions with vehicles e.g. separated cycleways. They also tend to have road rules that support cycling e.g. low speed limits. In the Netherlands, there’s also a presumption that drivers who collide with a child cyclist are at fault (see Are Dutch motorists strictly liable if they collide with a cyclist? ). Safety in numbers. As Statista argues, large numbers of cyclists means motorists expect to see riders more frequently and adjust their driving behaviour accordingly. Motorists are cyclists too. In places where cycling’s mode share is very high, there’s a higher likelihood that the average driver also cycles and hence can empathise with riders. Culture. In countries with a long history of cycling, motorists are more likely to acknowledge and accept the legitimate place of riders on roads and treat them respectfully. Selection. Risk-takers constitute a high proportion of riders in low cycling countries like Australia. In contrast, the risk profile of riders in places like the Netherlands is necessarily a closer match to the relatively more risk-averse profile of the population.

All of these contribute independently to varying degrees but it’s complicated by feedback loops galore. It’s unclear how important each one is, but I think number two, safety in numbers, is probably the least important. In any event it’s probably the density of cyclists that matters more than the numbers (see Cycling: is the Safety in Numbers effect all about the numbers?).

On the other hand, I think the selection effect is under-appreciated. Risk takers are over-represented on Australian roads. We know this because riders who suffer serious injury are mostly “lycra louts”; almost 70% were wearing cleated shoes at the time of their crash (see Should cyclists need a licence to ride on public roads?). Moreover, close to a third of cycling fatalities are due to ill-health e.g. heart attacks triggered by exertion (see Is it just vehicles or are MAMILs killing themselves too?).

Compare that with the Netherlands. In a city like Amsterdam where 38% of all trips are made by bicycle, the vast majority of travellers aren’t likely to be risk-takers; they’re people who cycle on roads in order to get places, not for fitness or sport. The average Dutch rider is accordingly more cautious than the average Australian rider.

While it’s hard to disentangle the variables that make for safer cycling, I think improving infrastructure is the key action (see Do more bikeways mean more bicycle commuting? and Does cycling infrastructure reduce serious accidents?). By reducing the scope for conflict between motorists and riders, infrastructure increases riders’ sense of subjective safety and encourages new cohorts to take up riding for transport. That in turns puts pressure on politicians to regulate negative driver behavior and invest in more infrastructure. New cohorts of riders will necessarily be more risk-averse than current generations.