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Childhood Injury Prevention Interventions
Environmental Changes
Background
The difficulty with changing behavior, particularly children’s
behavior, makes environmental modification particularly attractive. Changes in the
traffic environment have been a traditional component of pedestrian safety programs
for many years. Comprehensive programs, such as those in Europe, often go under
the rubric of "traffic calming" to denote efforts to slow down traffic,
thereby improving safety as well as the aesthetics of the environment.
Traffic calming refers to a group of measures designed to control traffic in an
urban residential area. The definition of traffic calming adopted at the 1997 international
ITE conference is, "the combination of mainly physical measu res that reduce
the negative effects of motor vehicle use, alter driver behavior and improve conditions
for non-motorized street users." (ITE 2001).
Measures are designed to reduce the number of commuters using residential streets
and to reduce the speed of remaining traffic. Measures can include establishing
a hierarchical road system, improving main roads to carry additional traffic and
restricting or removing traffic from residential streets with road closures or one-way
designations. Environmental changes designed to reduce speed include vertical changes
in the street (speed cushions, humped pelican crossings, raised junctions), lateral
changes in the street (off-set intersections), constrictions (narrowings, pinch
points, pedest rian refuges), gateways at the entrances to the area, build-outs
to protect on-street parking spaces, and mini-roundabouts (traffic circles).
Epidemiological studies of environmental risk factors for child pedestrian injury
indicate that the likelihood of injury increases for the following conditions: increase
in traffic volume (13-14 times) or speed limit (6 times), absence of play areas
(5.3 times), poorly protected play area (3.5 times) and high proportion of curbside
parking (3.4 times) (Roberts 1995,Wazana 1997).
In this current update (August 2001) we have included a meta-analysis of traffic
calming articles published between 1971 and 1994. Additionally, we limited individual
articles to those that reported changes in bicycle and pedestrian conflicts or injuries
as outcomes. This update excluded individual articles that report changes in traffic
volume, motor vehicle speed, or injuries to motor vehicle drivers or occupants,
(Brilion 1990, Retting 2001, Kaplan 2000,Corben 1996, Mountain 1989, Engel 1992, Vis 1992, Aljanahi 1999, Cloke, TRL 1999, Holland
1996, Chorlton 1990).
Review of environmental change interventionsn
(traffic calming):
Author | Elvik, 2000 |
Study design and target population | Meta-analysis of 33 articles.
Published from 1971-1994
Studies Include:
1-before-and after study design with matched comparison group.
2-before-and-after study design with general comparison group.
3-Simple before-and-after design with no comparison group. |
Intervention | Traffic calming defined as measures
to discourage non-local traffic from using residential streets and reducing
speed of remaining traffic. |
Outcomes | Traffic volume data by type of road
before and after.
Traffic volume for whole area before and after.
Accident severity for injury and non-injury (property damage)
accidents.
Effects stated only for whole area.
Effects stated for main roads. |
Results | Area wide traffic calming re duces
the number of accidents by 15% in area affected by traffic calming (main and
local roads combined).
Validity ratings assigned to studies. Statistical analysis
included random and fixed effects models, tests for heterogeneity of effects
and publication bias. |
Study quality and conclusions | All studies were non-experimental
before and after designs.
None of studies controlled for regression to the mean or long term
trends in accident occurrence.
Studies from 8 countries indicate traffic calming reduces
accidents. |
Author | Hyden, 2000 |
Study design and target population | Ecologic time-trend study design.
Vaxo, Sweden
4 months and 4 years post construction. |
Intervention | Small traffic roundabouts. |
Outcomes | Police accident reports, conflicts
(cars giving way to other cars, bikes or pedestrians), predicted number of injury
accidents, car speeds measured with radar guns. |
Results | 44% decrease in accident risk for
pedestrians and bicyclists. |
Study quality and conclusions | Size of roundabout should be as small
as possible; one car lane on entrance, circulation area and exit.
Slowing MV speed reduces pedestrian injuries. |
Author | Garder, 1998 |
Study design and target population | Meta-analysis of 33 articles.
Published from 1971-1994
Ecologic study design.
Gothenburg, Sweden. |
Intervention | Construction of raised urban bicycle
crossings at 44 road intersections.
Comparison group of conventional (unmodified) intersections. |
Outcomes | Accidents obtained from police reports
and hospital visits. (bicycle and pedestrian injuries recorded).
Bicycle volume and speeds,
MV speeds, conflicts between bicycles, MV, pedestrians at
road intersections. |
Results | Raised bicycle crossing reduced accident
risk by 30% compared to conventional bicycle crossing. Some evidence that pedestrians
and motorists also benefited.
Motorists speed reduced; increased bicycle volume on modified roadways;
conflicts reduced from 39 per 100 hours of observation before reconstruction
to 20 per 100 hours after. Biggest gain for pedestrian; conflicts involving
pedestrians decreased. |
Study quality and conclusions | Analysis incorporated increase in
bicycle exposure (volume).
Environmental changes reduced MV speed and thus bike and pedestrian
conflicts & injuries.
Increased bicycle speeds and riding against allowed direction
on bike paths increased bike injuries. |
Author | Webster, 1996 |
Study design and target population | Ecologic (before/after study) in UK.
Injuries measured in 72 traffic calming areas; speed data
recorded in 32 such areas. |
Intervention | 20 mph zones established in 200 residential
areas;
Traffic speed reduced by environmental measures. |
Outcomes | Accidents, speed data. |
Results | 61% reduction in total injuries.
70% reduction in child pedestrian injuries.
48% reduction in child cyclist injuries.
Speeds reduced by 9 mph (from 34 mph to 25 mph). |
Study quality and conclusions | Public reactions favorable.
Long period of data collection, but no control community was
used. Study provides some evidence that changing urban environment reduces
child pedestrian injuries. |
Author | Mackie, 1998 |
Study design and target population | Ecologic mixed study.
5 towns in England with intervention; 5 control areas. |
Intervention | Urban Safety Project. |
Outcomes | |
Results | 10% accident reduction overall; most
benefited are pedestrians, particularly children, and cyclists. |
Study quality and conclusions | Use of control areas adjusts for secular
trend and changes in traffic volume. |
Author | Schnull, 1992 |
Study design and target population | Ecologic study design.
Nordrhein-Westfallen, Germany, 1983-1990. |
Intervention | Speed reduction measures on 28 roads. |
Outcomes | Speed measurements.
Accidents and injuries involving MV pedestrians and bicyclists. |
Results | Number of injuries involving pedestrians
and bicyclists too small to evaluate. |
Study quality and conclusions | Description of various interventions
to reduce speed. No data presented to show that any individual measures or the
total package were effective |
Author | Box, 1989 |
Study design and target population | Ecologic time trend study design.
Naperville, IL. |
Intervention | Street lighting, 1984-85 vs 1986-87. |
Outcomes | Night accident reduction rates. |
Results | Night accident reduction of 36%.
Night-time proportion of pedestrian bicycle accidents reduced
42% mid-block and 17% at intersections.
Lighting cost effective after 1 year. |
Study quality and conclusions | Adjusted for average daily traffic
volume.
Study illustrates the benefits of properly designed modern
lighting. |
Author | Engel and Thomsen, 1992 |
Study design and target population | Before-after study with control group
Denmark, countrywide |
Intervention | Traffic calming, with special focus
on making some streets priority for pedestrians with speeds of 15 km/hr. In
addition, other streets were set at 30 km/hr. |
Outcomes | Police-reported pedestrian-MV collisions
and collisions involving pedestrian injury |
Results | Per kilometer of road: On streets
designated as 30 km/hr, 24% reduction in pedestrian-MV collisions and 45% reduction
in pedestrian injuries.
Per kilometer traveled by road user: 72% reduction
in pedestrian injuries (OR=0.28, 0.08-0.96).
For speed bumps, they calculated that for every 1 cm increase
in the height of the bump, there is a 1 km reduction in speed.
Narrowing a road will decrease the speed by about 5 km/hr |
Study quality and conclusions | The study is one of a series from
Scandinavia and Europe indicating that traffic calming techniques can reduce
speed and decrease the risk of injuries.
No separate data for children. Data appear to be reliable
since they are based on police reports. |
Author | Van Houten and Malenfant, 1992 |
Study design and target population | Before-after design
Motorists and pedestrians (all ages) in Dartmouth, Nova Scotia. |
Intervention | Signs prompting drivers to stop farther
back from the crosswalk to increase visibility of pedestrian to other drivers
with or without line on pavement indicating where to stop |
Outcomes | (1) distance from crosswalk at which
car stopped;
(2) driver yielding to pedestrian;
(3) pedestrian-MV conflicts |
Results | (1) OR for stopping less than 30 feet
from crosswalk was 0.63 for sign; addition of line made little difference;
(2) OR for pedestrian-MV conflicts was 0.40-0.47 following introduction
of sign, and 0.19-0.24 following sign plus line. Intervention was equally
effective whether or not pedestrian-activated flashing light was used.
(3) The odds of drivers not yielding to pedestrian was 0.86-0.89
after the sign; line had no added benefit. |
Study quality and conclusions | The results indicate that the sign
did decrease all 3 hazards to pedestrians; with the exception of pedestrian-MV
conflicts, line added little. Effects were maintained one month and one year
later.
Study had before-after data only; no control groups. |
Author | Vis et al., 1992 |
Study design and target population | Non-equivalent control group design
15 experimental areas in the Netherlands. |
Intervention | Use of traffic calming measures to
lower speeds to 30 km/hr: signs, speed bumps, narrowing the road, entrance constructions,
partial barricades, pedestrian refuges. |
Outcomes | Reduction in speed
Reduction in traffic volume.
Police reported MV collisions and collisions with injuries. |
Results | Reduction in speed by: humps-40% reduction;
narrowed entrance-28%; speed bump-25%; mini roundabout-25%; diagonal closure
of street-23%. Signs only did not reduce speed. However, effect of measure varied
enormously from one area to another.
Traffic volume decreased by 5-30%.
Injuries from MV crashes decreased by 20% (OR=0.80). |
Study quality and conclusions | The measures appeared to slow the
speed of traffic and reduce the number of injuries. However, the effect appears
to be highly variable. This may be due to the small sample size. In addition,
pedestrian injuries and child injuries are not separated out. |
Author | Garder, 1989 |
Study design and target population | Signalization at 115 intersections
in Stockholm and Malmoe, Sweden
Use of traffic conflicts technique on 1728 observations |
Intervention | Traffic signals at intersections |
Outcomes | Number of pedestrian motor vehicle
conflicts as a proxy for pedestrian-MV collisions. |
Results | In general, at intersections with
mean speed >30km/hr, signalization appears to reduce the risk of pedestrian
injury by 50%. Pedestrian refuges decrease risk of injury by about 30%. |
Study quality and conclusions | No data specifically on children.
No actual injury data. Number of observations for particular kinds of intersections
was small. No multi-variate analysis. |
Summary of environmental modification programs:
There are no randomized controlled trials of traffic calming, and
some of the studies use only before-after comparisons, thus not accounting for secular
trends. The majority of the studies are from 7 European countries, the remainder
from Australia, Canada and the United States. Outcome measures vary among the studies
and data specifically on children are largely absent.
Despite these concerns, traffic calming appears to be a promising intervention.
It not only reduces the risk of injuries, but also makes the cities more esthetically
pleasing. The success of traffic calming is best illustrated by the Elvik 2000 meta-analysis which found area-wide urban
traffic calming schemes reduced the number of injury accidents by 15% (25% on residential
stree ts and 10 % on main roads). This figure is currently the best estimate of
the effect of traffic calming. Studies reporting higher success rates are in general,
weak designs without comparison groups.
Changes in transport policy to encourage walking and cycling for short trips and
bus, train, air trips for longer distances should be considered. (Roberts 1995)
This would include environmental changes to make walking safer and a philosophical
shift to value pedestrian and cyclists' convenience over that o f motor vehicle
drivers.
Recommendations on environmental modifications:
These are recommended as being a probably effective
pedestrian injury prevention strategy. They will fit nicely with the Haddon matrix
and the general principles of passive vs. active strategies.
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