Study Finds Red-Light Cameras to Be Effective at Reducing About 30 Percent of Rear-End and Right-Angle Crashes with a Benefit-to-Cost Ratio of 2.61.
University Researchers Evaluated Red-Light Cameras Installed in the Chicago Regional Area.
Made Public Date
08/26/2021

1177

Chicago, Illinois,
United States
Identifier
2021-01588
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Spillover Effect and Economic Effect of Red-Light Cameras

Summary Information

This study analyzed intersections throughout the city of Chicago (including Du Page, Lake, Kane, and Cook counties) where red-light cameras (RLCs) were installed. The “spillover effect,” or the expected safety improvements at intersections without RLCs, was estimated for selected intersections. A total of 84 signalized intersections, including 60 signalized intersections adjacent to an RLC-treated intersection and 24 random intersections throughout Chicago were analyzed. The following crash data were analyzed: rear-end intersection-related, rear-end non-intersection-related, right-angle intersection-related, and right-angle non-intersection-related crashes. Crash occurrence and severity reductions were calculated to quantify the spillover effect. The benefits and costs of RLC installation and the economic benefits of RLCs were also calculated to determine their safety and cost effectiveness. The “before” period covered three years immediately before the RLC installation year while the “after” period covered three years immediately after. This study was conducted from August 16, 2016 to April 15, 2017.

METHODOLOGY  

Economic benefits were calculated as an equivalent uniform annual benefit (EUAB) and crash costs were calculated as an equivalent uniform annual cost (EUAC) based on Illinois Department of Transportation’s (IDOT) values. A naïve study that assumes the expected crash frequency in the after-modification period to be

the crash frequency in the before period was used to estimate crash reduction between before and after periods. An Empirical Bayes analysis that utilized applicable safety performance functions (SPF) was used to estimate safety effectiveness. When evaluating safety effectiveness, crashes were organized using the KABCO injury classification (K – Fatal; A – Incapacitating injury; B – Nonincapacitating injury; C – Possible injury; and O – No injury). The crash cost of each category was estimated using a weighted average across different crash types.

FINDINGS

Both rear-end and right-angle crashes were reduced about 30 percent at adjacent and randomly selected intersections. Using the naïve approach, total rear-end crashes were reduced by 30.6 percent and right-angle crashes were reduced by 35.1 percent. Using the Empirical Bayes method, total rear-end crashes were reduced by 26.1 percent and right-angle crashes were reduced by 31.7 percent.  Crashes of most severities, excluding B (Nonincapacitating injuries) were reduced. Severity reductions for crashes at adjacent and randomly selected intersections are summarized in the table below.

Crash severity reductions at adjacent and random intersections based on Naïve Study.

Crash Type

Crash Severity

Percent Reduction

Rear-End Intersection-Related

K

A

27.27%

B

4.76%

C

9.74%

PDO*

43.65%

Rear-End Non-Intersection-Related

K

A

46.00%

B

-15.00%

C

-3.33%

PDO*

33.01%

Right-Angle Intersection-Related

K

A

51.92%

B

11.33%

C

13.08%

PDO*

38.87%

Right-Angle Non-Intersection-Related

K

Sample size too small

A

40.00%

B

-90.00%

C

22.73%

PDO*

30.36%

* Property Damage Only (PDO)

Using the number of K/A/B and C/O annual crashes before and after RLC installation, the EUAB is $668,645. With a calculated EUAC of $259,370, the benefit/cost ratio was calculated at 2.61.

 

 

Goal Areas
Results Type