Exploring the safety in numbers effect for vulnerable road users on a macroscopic scale

Area of Science:

• Urban planning
• Transportation engineering
• Public health

Background:

• The "safety in numbers" effect suggests that increased numbers of road users correlate with a reduced crash rate per user.
• This principle is often cited to advocate for multimodal transportation infrastructure to promote walking, cycling, and public transit.
• Understanding this effect is crucial for designing safer and more sustainable urban environments.

Purpose of the Study:

• To investigate the "safety in numbers" effect for pedestrians and cyclists.
• To analyze this effect in urban areas with varying levels of multimodal infrastructure access.
• To provide empirical evidence for the benefits of multimodal transportation investments.

Main Methods:

• Utilized crash data from Chicago, analyzing it at the census tract level.
• Applied Generalized Additive Models (GAM) to account for spatial dependencies in crash occurrences.
• Modeled travel exposure using metrics like trip generation, multimodal infrastructure availability, network characteristics, and accessibility.

Main Results:

• Confirmed the existence of a "safety in numbers" effect on a macroscopic level.
• The effect was observed for motor vehicles, pedestrians, and bicyclists.
• Findings indicate that increased user numbers are associated with a disproportionately lower increase in crashes.

Conclusions:

• The "safety in numbers" phenomenon is empirically supported for various road users, including pedestrians and cyclists.
• This research validates the rationale for investing in multimodal transportation systems.
• Promoting active transportation and public transit can lead to enhanced road safety in urban settings.