U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
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| Publication Number: FHWA-HRT-17-084 Date: February 2018 |
Publication Number: FHWA-HRT-17-084 Date: February 2018 |
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The research documented in this report was conducted as part of the Federal Highway Administration’s (FHWA’s) Evaluation of Low-Cost Safety Improvements Pooled Fund Study (ELCSI-PFS). FHWA established this PFS in 2005 to conduct research on the effectiveness of the safety improvements identified by the National Cooperative Highway Research Program Report 500 Guides as part of the implementation of the AASHTO Strategic Highway Safety Plan. The ELCSI-PFS studies provide a crash modification factor and benefit–cost economic analysis for each of the targeted safety strategies identified as priorities by the pooled fund member States.
This study evaluates corner clearance at signalized intersections in the State of California and the City of Charlotte, North Carolina. For limited corner clearance on the approach corners, the results indicate statistically significant reductions in total, fatal and injury, and rear-end crashes. The results also indicated reductions in sideswipe and nighttime crashes, and increases in right-angle and turning crashes. This study suggests that removing access on mainline receiving corners to improve corner clearance—with reasonable assumptions for cost, service life, and the value of a statistical life—can be cost effective for reducing crashes at signalized intersections. This document is intended for safety engineers, highway designers, planners, and practitioners at State and local agencies involved with AASHTO Strategic Highway Safety Plan implementation.
Jonathan Porter, Ph.D.
Acting Director, Office of Safety
Research and Development
Notice
This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.
The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.
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Technical Report Documentation Page
| 1. Report No.
FHWA-HRT-17-084 |
2. Government Accession No.
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3 Recipient's Catalog No.
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| 4. Title and Subtitle
Safety Evaluation of Corner Clearance at Signalized Intersections |
5. Report Date
February 2018 |
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| 6. Performing Organization Code
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| 7. Author(s)
Thanh Le, Frank Gross, Tim Harmon, and Kimberly Eccles |
8. Performing Organization Report No.
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| 9. Performing Organization Name and Address
VHB |
10. Work Unit No. (TRAIS)
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| 11. Contract or Grant No.
DTFH61-13-D-00001 |
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| 12. Sponsoring Agency Name and Address
U.S. Department of Transportation |
13. Type of Report and Period Covered
Final Report; June 2015–September 2017 |
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| 14. Sponsoring Agency Code
HRDS-20 |
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| 15. Supplementary Notes
The Federal Highway Administration (FHWA) Office of Safety Research and Development managed this study under the Development of Crash Modification Factors (CMFs) program. The FHWA Office of Safety Research and Development Program and Task Manager was Ms. Roya Amjadi (HRDS-20). |
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| 16. Abstract
This study evaluates corner clearance at signalized intersections under the Development of Crash Modification Factors program for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. Geometric, traffic, and crash data were obtained for signalized intersections with various corner clearances from the State of California and the City of Charlotte, North Carolina. A cross-sectional analysis was conducted to estimate the effects of corner clearance while controlling for other differences among study sites. The estimated CMFs indicated that more limited clearance (i.e., driveway(s) within 50 ft of the signalized intersection) on receiving corners was associated with increases for all crash types, based on the data included in this analysis. These increases were statistically significant at the 90-percent level or greater for total, fatal and injury, rear-end, sideswipe, right-angle, and nighttime crashes. Only the results for turning crashes were not statistically significant at the 90-percent level. For limited corner clearance on the approach corners, the results indicated statistically significant reductions in total, fatal and injury, and rear-end crashes. The results also indicated reductions in sideswipe and nighttime crashes, and increases in right-angle and turning crashes, but none of these results were statistically significant at the 90-percent level. |
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| 17. Key Words
Corner clearance, signal, intersection, low-cost, safety improvements, safety evaluations, access management, driveways |
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. |
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| 19. Security Classification (of this report)
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20. Security Classification (of this page)
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21. No. of Pages
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22. Price
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| Form DOT F 1700.7 (8-72) | Reproduction of completed page authorized |
SI* (Modern Metric) Conversion Factors
Figure 1. Photo. Signalized intersection with limited receiving corner clearance
Figure 2. Schematic. General layout of study site
Figure 3. Screenshot. Select study location in Google® Earth™ (circle added by research team to indicate intersection of interest)
Figure 4. Screenshot. Locate and verify intersection in HSIS data file
Figure 5. Screenshot. Example of Charlotte data layers in ArcGIS
Figure 6. Screenshot. Measuring corner clearance in Google® Earth™
Figure 7. Equation. Model for total crashes
Figure 8. Equation. Model for fatal and injury crashes
Figure 9. Equation. Model for rear-end crashes
Figure 10. Equation. Model for sideswipe crashes
Figure 11. Equation. Model for right-angle crashes
Figure 12. Equation. Model for turning crashes
Figure 13. Equation. Model for nighttime crashes
Figure 14. Screenshot. Intersection with limited approach corner clearance from Google® Maps™
Figure 15. Screenshot. Intersection with limited receiving corner clearance from Google® Maps™
Figure 16. Screenshot. Intersection with limited corner clearance on all mainline corners from Google® Maps™
Figure 17. Screenshot. Intersection without limited corner clearance on all mainline corners from Google® Maps™
Table 1. ZINB model estimation results adapted from Kwigizile et al.
Table 2. Crashes per site-year from data collection sites
Table 3. Data summary for signalized intersections and corner clearance
Table 4. Model parameters for total crashes
Table 5. Model parameters for fatal and injury crashes
Table 6. Model parameters for rear-end crashes
Table 7. Model parameters for sideswipe crashes
Table 8. Model parameters for right-angle crashes
Table 9. Model parameters for turning crashes
Table 10. Model parameters for nighttime crashes
Table 11. Results for total crashes
Table 12. Results for fatal and injury crashes
Table 13. Results for rear-end crashes
Table 14. Results for sideswipe crashes
Table 15. Results for right-angle crashes
Table 16. Results for turning crashes
Table 17. Results for nighttime crashes
Table 18. BC ratios for removing receiving corner access points from a site with limited clearance on two receiving corners
Table 19. Recommended CMFs for limited approach corner clearance
Table 20. Recommended CMFs for limited receiving corner clearance
| AADT | annual average daily traffic |
| B/C | benefit–cost |
| CMF | crash modification factor |
| DCMF | Development of Crash Modification Factors |
| ELCSI-PFS | Evaluation of Low-Cost Safety Improvements Pooled Fund Study |
| FHWA | Federal Highway Administration |
| FID | feature identifier |
| GIS | geographic information system |
| GPS | global positioning system |
| HSIS | Highway Safety Information System |
| KML | Keyhole Markup Language |
| NCHRP | National Cooperative Highway Research Program |
| PDO | property-damage-only |
| SE | standard error |
| USD | United States dollar |
| USDOT | United States Department of Transportation |
| ZINB | zero-inflated negative binomial |
