Table 2 Studies that investigated relationships between bicyclist safety and intersection-related transportation infrastructure

ROUNDABOUTS

Schoon and Van Minnen

(1994)

The safety of roundabouts in the Netherlands

[53]

The Netherlands;

Observational, before-after intervention

Roundabouts vs. other intersection types; and roundabout design features

181 intersections before and after implementation of roundabouts

National database of bicycle and moped injuries and crashes* (529 before, 111 after)

Change in crash and injury rates after intervention.

Corrected for the temporal trends in crash and injury rates across all intersections in the Netherlands: national data that showed a 2 to 13% decrease over the study period. A seven-month "transitional period" following roundabout construction was not included in before-after analysis.

8% reduction in bicyclists' crash rate and 30% reduction in injury rate were observed following installation of new roundabouts. Among the 3 styles of roundabouts, those with cycle tracks had the greatest reductions in injuries to cyclists and moped users (90%), compared to those with no bicycle infrastructure (41% reduction) and those with a cycle lane (25% reduction).

Brüde and Larsson (2000)

What roundabout design provides the highest possible safety?

[54]

Sweden;

Observational, non-intervention

Roundabouts vs. other intersection types

72 roundabouts with ≥ 100 cyclists/day

Police reports of 67 crashes*, 58 of which resulted in injuries

Comparison of observed and expected crash counts. Regression analyses to examine factors affecting crash counts and rates.

Calculated expected crashes and injuries using published prediction models for conventional intersections based on motor vehicle and bicycle traffic volumes.

At two-lane roundabouts, the observed crashes and injuries were more than twice those expected, whereas at single lane roundabouts there was no difference between expected and observed. Two other factors were associated with lower than expected crashes: single lane roundabouts with a central island radius > 10 m, and bicycle travel on bikeways rather than the roadway of the roundabout intersection.

Hels and Orozova-Bekkevold

(2007)

The effect of roundabout design features on cyclist crash rate

[55]

Denmark - Odense; Observational, non-intervention

Roundabout design features

88 roundabouts

Police reports and Emergency Department records of 152 injuries*

Poisson regression and logistic regression analyses between cyclist injuries (3/year and probability, respectively) and roundabout characteristics: geometry, age, traffic volume (vehicles and cyclists), and location (urban/rural).

Adjusted for temporal changes in traffic volume.

In multiple regression, higher vehicle and cyclist traffic volumes and "drive curve" (a proxy for vehicle speed) were associated with higher numbers of cyclist crashes/year.

Daniels et al. (2008)

The effects of roundabouts on traffic safety for bicyclists: An observational study

[56]

Belgium - Flanders;

Observational, before-after intervention

Roundabouts vs. other intersection types

91 intersections before and after implementation of roundabouts (40 inside built-up areas with speed limit of 50 km/h, and 51 in areas with speed limits of 70 or 90 km/h)

Police reports of 1060 injuries (411 at roundabouts, 649 at comparison intersections)

Effectiveness index = odds ratio for the before-after change in injury rates of the roundabout intersections as compared to the change in injury rates at conventional comparison intersections.

Comparison group: unchanged conventional intersections near intervention sites to account for temporal trends in safety and regression-to-the-mean (e.g. intersections may have been selected for roundabout construction because of higher numbers of crashes).

Roundabouts have the effect of increasing risk of crashes resulting in injury at or near the intersection (odds ratio = 1.27). The effect is stronger for intersections inside built-up areas (odds ratio = 1.48).

Daniels et al. (2009)

Injury crashes with bicyclists at roundabouts: influence of some location characteristics and the design of cycle facilities

[57]

Belgium - Flanders;

Observational, before-after intervention

Roundabouts vs. other intersection types

Same data as Daniels 2008, above, except only 50 intersections in areas with speed limits of 70 or 90 km/h)

Same data as Daniels 2008, above.

Effectiveness index as Daniels 2008, above. Regression models to evaluate the roundabout design determinants of the effectiveness index.

Same data as Daniels 2008, above.

Roundabouts with cycle lanes had significantly higher risk (odds ratio = 1.93), whereas no increased risks were observed for roundabouts with mixed traffic, separate cycle tracks, or grade-separated paths. Roundabouts with 2 lanes and those replacing signalized intersections also had elevated risks.

BICYCLE CROSSINGS

Gårder et al. (1998)

Measuring the safety effect of raised bicycle crossings using a new research methodology

[58]

Sweden - Gothenburg;

Observational, before-after intervention

Bicycle crossings (raised above road level by 4-12 cm) vs. other intersection types

44 intersections (and 18.7 km of adjacent road sections) before and after implementation of raised bicycle crossings

Police or hospital reports of 287 crashes* (160 before, 127 after)

Calculated unadjusted number of crashes per month after intervention compared to before intervention.

Adjusted for traffic volume data collected on 2 intervention streets and 2 unchanged streets.

There was an 8% increase in crash frequency in the study area, but bicycle volume on these intervention sections grew by 50% more than unchanged streets - authors conclude that the intervention may have resulted in a safety improvement.

Jensen (2008) Safety effects of blue cycle crossings: a before-after study

[59]

Denmark - Copenhagen;

Observational, before-after intervention

Bicycle crossings (colored blue) vs. other intersection types

65 intersections before and after implementation of blue bicycle crossings

Police reports of 567 injuries (319 before, 248 after); 1,595 collisions (778 before, 817 after)

Comparison of observed injuries and crashes with expected (using fixed and random effects models).

Adjusted for temporal trends in traffic volumes and crashes, based on data from changed and unchanged intersections. Considered regression-to-the-mean, but no adjustment was deemed necessary.

Risk of crash/injury depends on number of colored crossings: 1 crossing = 10% reduction for injuries/19% for crashes; 2 crossings = 23%/48% increase; 4 crossings = 60%/139% increase. Authors hypothesize that non-intuitive findings may result from motorist confusion at sites with many crossings.

INTERSECTION DESIGN

Wang and Nihan (2004)

Estimating the risk of collisions between bicycles and motor vehicles at signalized intersections

[60]

Japan - Tokyo†;

Observational, non-intervention

Intersection design, including number of turn lanes, width of medians, pedestrian overpass

115 randomly selected signalized intersections with 4 legs

Police-reports of 585 bicycle-motor vehicle collisions

Three Poisson models of crash event risk: for "through" motor vehicle travel; left-turn travel; and right-turn travel.

Adjusted for average bicycle and motor vehicle volume, intersection location, speed limit, visual noise.

A higher number of turning lanes and presence of a wide median significantly increased risk of crash during motor vehicle turning maneuvers. Narrower entering approaches and wider medians increased crash risk in certain turning collisions. Increased cycle volumes were associated with lower collision risk with turning vehicles.