Benefit

Dynamic roadside warning systems that alert drivers of opposing traffic at rural intersections can decrease roll-throughs up to 22 percent.

Experience evaluating an intersection collision warning system in Duluth, Minnesota.


February 2014
Intersection of Lismore Rd and Lakewood Rd.,Duluth,Minnesota,United States


Summary Information

This study evaluated the impacts of a dynamic warning system developed to improve safety at intersections having limited sight distance in Duluth, Minnesota. Using vehicle detectors, wireless communications, and signs with LED flashers the system alerted drivers of potential conflicts with opposing traffic at a two-way stop intersection obscured by hilly terrain.

The system dubbed ALERT (Advanced LED Warning System for Rural Intersections) was implemented and evaluated in two phases. Experience gained from the first deployment (ALERT-1) was used to improve the second deployment (ALERT-2). Both applications included Cross Traffic warning signs with blinking LEDs on the main highway, Vehicle Approaching warning signs with LEDs on minor approaches, and a set of non-intrusive sensors and wireless communications needed to activate and deactivate blinking LEDs.

The design of the ALERT-2 system included additional LED blinkers on minor roadway stop signs to further reduce intersection roll-throughs that were frequently observed during no-conflict conditions. These blinkers were activated when a vehicle passed a Stop Ahead sign located upstream from the intersection, and then deactivated when the vehicle arrived at the stop sign.

METHODOLOGY

Field Testing

ALERT-1 and ALERT-2 testing were conducted at two separate locations to eliminate potential skewed results from driver learning effects. This report focused on findings from ALERT-2 but referenced ALERT-1 for comparison purposes. Traffic and video data were collected before and after ALERT-2 was installed. Prior to installation, 42 days of traffic data and 15,893 vehicle movements were recorded from June 26 to August 15, 2011. After installation 258 days of traffic data and 117,854 vehicle movements were recorded from September 5, 2011 to June 26, 2013.

Traveler Surveys

Surveys were mailed to local residents living within a two mile radius of the intersection. Each letter included a short explanation of the purpose of the survey, five short questions, and free space for comments. A pre-stamped self addressed return envelope was included with each survey letter to encourage participation and anonymity. A total of 206 letters were sent out, and 119 (58 percent) surveys were completed and returned.

FINDINGS

Field Testing
  • After ALERT-1 and ALERT-2 features were installed, roll-throughs decreased by 22 percent.
Traveler Survey
  • The ALERT-2 mail-in survey found that 92 percent of respondents either "strongly agreed" or "agreed" that the system improved safety at the intersection. Previously, during the ALERT-1 project this number was 72 percent.
  • Overall, 87 percent of respondents rated the effectiveness of the warning system as excellent or good.
The table below excerpted from the source report highlights findings from the ALERT-2 mail-in survey. Results show the Number of respondents (and percent of total).

1. On average, how many times a day do you travel through the intersection of Lismore Road and Lakewood Road?
0
1
2
3+
13
(11%)
24
(20%)
55
(46%)
27
(23%)

2. How much do you agree with the following statements:
Strongly Agree
Agree
Disagree
Strongly Disagree
2a) The warning system is easy to understand.
65
(55%)
46
(39%)
6
(5%)
2
(1%)
2b) The warning system improved the safety of the intersection.
67
(56%)
43
(36%)
1
(1%)
8
(7%)
2c) The vehicle activated Blinker STOP signs obtain my attention.
83
(70%)
34
(28%)
1
(1%)
1
(1%)
2d) The warning system could be used at other intersections.
63
(53%)
45
(38%)
6
(5%)
5
(4%)

3. How would you rate the overall effectiveness of the warning system?
Excellent
Good
Fair
Poor
62
(52%)
42
(35%)
10
(9%)
5
(4%)

*

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Source

Advanced LED Warning System for Rural Intersections: Phase 2 (ALERT-2)

Author: Kwon, Taek M. and Husam Ismail

Published By: Minnesota Department of Transportation

Prepard by the University of Minnesota, Duluth MnDOT

Source Date: February 2014

Other Reference Number: Report No. MN/RC 2014-10

URL: http://www.its.umn.edu/Publications/ResearchReports/pdfdownload.pl?id=2448

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Goal Areas

Safety

Typical Deployment Locations

Rural Areas

Keywords

None defined

Benefit ID: 2014-00930