Safety in numbers
Encyclopedia
Safety in numbers is the hypothesis that, by being part of a large physical group or mass, an individual is proportionally
less likely to be the victim of a mishap, accident
, attack, or other bad event. Some related theories also argue (and can show statistically) that mass behaviour (by becoming more predictable and "known" to other people) can reduce accident risks, such as in traffic safety - in this case, the safety effect creates an actual reduction of danger, rather than just a redistribution over a larger group.
of birds and schooling
of fish. In both of these instances, by being part of a large group, individuals face less risk
of falling victim to predators than they would if traveling alone.
or cyclist, becomes less likely to be involved in a crash, as the population of similar road users increases. A Public Health Consultant has concluded that the theory is correct, based on statistical analysis of collision data.
A 2002 study into whether pedestrian risk decreased with pedestrian flow, using 1983-86 data from signalized intersections in a town in Canada, found that in some circumstances the risk per pedestrian decreased with increased pedestrian flow.
.
Another author has written that, while such data shows a degree of correlation, conclusions of causality
may very well be based on a statistically spurious relationship
. In other words, the relationship of an increase in bicycle use and a decrease in cyclist injuries may have no actual causal connection due to a certain third, unseen factor (referred to in statistics as a "confounding factor" or "lurking variable"). A spurious relationship gives an impression of a worthy link between two groups that is invalid when objectively examined.
Charles Komanoff has concluded that in "diluting the effect of 'safety in numbers,' compulsory helmet laws could have the perverse effect of increasing serious injury rates among those who continue to cycle."
In the United Kingdom, Transport for London
, the body responsible for the London Congestion Charge
, stated in their April 2005 review of that scheme, that motor vehicle traffic had decreased by 16%, bicycle use had increased by 28% and cyclist injuries had decreased by 20% in the first year of operation of the scheme.
In January 2008, a London newspaper reported that the number of cyclists in London being treated in hospitals for serious injuries had increased by 100% in six years. Over the same time, they report, the number of cyclists had increased by 84%.
Between 1992 and 2008, the number of bicyclists crossing four bridges into downtown was measured to have increased 369% between 1992 and 2008. During that same period, the number of reported crashes increased by only 14%.
Proportionality (mathematics)
In mathematics, two variable quantities are proportional if one of them is always the product of the other and a constant quantity, called the coefficient of proportionality or proportionality constant. In other words, are proportional if the ratio \tfrac yx is constant. We also say that one...
less likely to be the victim of a mishap, accident
Accident
An accident or mishap is an unforeseen and unplanned event or circumstance, often with lack of intention or necessity. It implies a generally negative outcome which may have been avoided or prevented had circumstances leading up to the accident been recognized, and acted upon, prior to its...
, attack, or other bad event. Some related theories also argue (and can show statistically) that mass behaviour (by becoming more predictable and "known" to other people) can reduce accident risks, such as in traffic safety - in this case, the safety effect creates an actual reduction of danger, rather than just a redistribution over a larger group.
Description
Evidence often advanced for this position includes the flockingFlocking (behavior)
Flocking behavior is the behavior exhibited when a group of birds, called a flock, are foraging or in flight. There are parallels with the shoaling behavior of fish, the swarming behavior of insects, and herd behavior of land animals....
of birds and schooling
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
of fish. In both of these instances, by being part of a large group, individuals face less risk
Risk
Risk is the potential that a chosen action or activity will lead to a loss . The notion implies that a choice having an influence on the outcome exists . Potential losses themselves may also be called "risks"...
of falling victim to predators than they would if traveling alone.
In road traffic safety
Safety in numbers is also used to describe the theory that a particular road user, especially a pedestrianPedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...
or cyclist, becomes less likely to be involved in a crash, as the population of similar road users increases. A Public Health Consultant has concluded that the theory is correct, based on statistical analysis of collision data.
Research
There are several studies and reports which address this idea.A 2002 study into whether pedestrian risk decreased with pedestrian flow, using 1983-86 data from signalized intersections in a town in Canada, found that in some circumstances the risk per pedestrian decreased with increased pedestrian flow.
Criticism
A Cycling Transportation Engineer has disputed that conclusion, writing that the data used is insufficient to demonstrate that there is a cause-and-effect relationshipCausality
Causality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....
.
Another author has written that, while such data shows a degree of correlation, conclusions of causality
Causality
Causality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....
may very well be based on a statistically spurious relationship
Spurious relationship
In statistics, a spurious relationship is a mathematical relationship in which two events or variables have no direct causal connection, yet it may be wrongly inferred that they do, due to either coincidence or the presence of a certain third, unseen factor In statistics, a spurious relationship...
. In other words, the relationship of an increase in bicycle use and a decrease in cyclist injuries may have no actual causal connection due to a certain third, unseen factor (referred to in statistics as a "confounding factor" or "lurking variable"). A spurious relationship gives an impression of a worthy link between two groups that is invalid when objectively examined.
Helmet debate
Safety-in-numbers is important in the debate over the efficacy of bicycle helmets, because compulsory helmet laws have been shown to discourage bicycling.Charles Komanoff has concluded that in "diluting the effect of 'safety in numbers,' compulsory helmet laws could have the perverse effect of increasing serious injury rates among those who continue to cycle."
Finland
After cycling was promoted in Finland, the number of trips increased by 72% and there was a 75% drop in cyclists deaths.London, UK
Between 2000 and 2008, the number of bicycle trips made in London, UK doubled. Over the same period, serious bicycle injuries declined by 12%.In the United Kingdom, Transport for London
Transport for London
Transport for London is the local government body responsible for most aspects of the transport system in Greater London in England. Its role is to implement the transport strategy and to manage transport services across London...
, the body responsible for the London Congestion Charge
London congestion charge
The London congestion charge is a fee charged for some categories of motor vehicle to travel at certain times within the Congestion Charge Zone , a traffic area in London. The charge aims to reduce congestion, and raise investment funds for London's transport system...
, stated in their April 2005 review of that scheme, that motor vehicle traffic had decreased by 16%, bicycle use had increased by 28% and cyclist injuries had decreased by 20% in the first year of operation of the scheme.
In January 2008, a London newspaper reported that the number of cyclists in London being treated in hospitals for serious injuries had increased by 100% in six years. Over the same time, they report, the number of cyclists had increased by 84%.
Berlin, Germany
Between 1975 and 2001, the total number of bicycle trips almost quadrupled. Between 1990 and 2007, the share of trips made by bicycle increased from 5% to 10%. Between 1992 and 2006, the number of serious bicycle injuries declined by 38%.Portland, Oregon, US
Between 1990 and 2000, the percentage of workers who commuted to work by bicycle rose from 1.1% to 1.8%. By 2008, the proportion has risen to 6.0%; while the number of workers increased by only 36% between 1990 and 2008, the number of workers commuting by bicycle increased 608%.Between 1992 and 2008, the number of bicyclists crossing four bridges into downtown was measured to have increased 369% between 1992 and 2008. During that same period, the number of reported crashes increased by only 14%.