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An Examination of Roadway Feature Identification Lighting versus Designed Lighting Systems

Description:

The proposed research project will consider the benefits and trade offs associated with roadway feature identification lighting versus designed lighting systems. (Note: roadway feature identification lighting generally refers to a single luminaire placed to identify a roadway element. Designed lighting systems refer to lighting systems designed to meet specific visibility requirements on the roadway.) The results of the research will provide guidance to the following design and operational decisions:

  1. Does the simple placement of a single luminaire to identify a geometric feature (curve, intersection, etc.) provide any safety benefits?
  2. Does a designed or engineered lighting arrangement offer significant benefits over a roadway feature identification lighting placement?

  3. Under what conditions should an engineered lighting system be put into service?

It is proposed that the work for this study would be carried out at intersections as considerable amounts of existing research on crash reductions at intersections. The work should result in recommendations that can be applied to other geometric features such as curves. The benefits of the research include support for the Illuminating Engineering Society of North America (IESNA) to create standards that will lead to better designed intersections as well as improve decision making about when to install lighting. Such information will help address the issue of how best to light an intersection which is currently in need of better quantification by the Illuminating Engineering Society of North America (IESNA). For example, near side lighting is recommended for pedestrians, but does not necessarily accommodate the visibility needs of drivers negotiating the intersection that would best be met by far side lighting. From this standpoint, there could be immediate payoff for intersection lighting design from this research. However, many of the principles that are examined and developed for intersections should have implications for other roadway features. The research should take the intersection focus and, to the extent possible, extend the findings to other features.

Objective:

The final product would be guidance on where and under what conditions simple roadway feature identification lighting is acceptable and recommendations for new or improved standards and design guidance for use by the Illuminating Engineering Society of North America.

Benefits:

Lighting is a known and significant safety countermeasure in all three of the FHWA safety focus areas (Horizontal Curves/Roadway Departure, Intersections, Pedestrians). For example, for rural intersections, the frequency of nighttime crashes for lighted intersections is half that of intersections without lighting. Fatalities at rural intersections at night are 39% of the total of 7,772 fatalities for 2008 (preliminary); Intersection fatalities under dark, dawn, and dusk are 14% + 2% + 2% = 18% of the 3,108 rural intersection fatalities or 559 fatalities nationally in 2008. Lighting as a countermeasure has the potential to reduce this number by half (280 fatalities a year) which has the benefit of $2.7 million per occurrence of averting an accidental fatality or $756 million annually for rural intersection alone.

Although the benefit of lighting for roadway features such as rural intersections is known, highway agencies direly need to know how to place roadway lighting for roadway features such as horizontal curves and intersections. Is one roadway feature luminaire (a destination light) at an intersection adequate to attain the benefit or is an engineered system of lighting needed to obtain the known crash reduction? The result of the proposed research project is the determination of the answer to this choice as a recommended practice associated with the countermeasure of roadway feature lighting.

Related Research:
  1. Roadway Lighting Shows Safety Benefits at Rural Intersections, Hillary N. Isebrands, P.E. S.M. ASCE1 and Shauna L. Hallmark M.ASCE2

Intersection-related crashes account for approximately 31% of fatal crashes in Minnesota and roughly 37% of those occurred at night, dusk, or dawn. Nationally, only 25 to 33% of the vehicle miles traveled (VMT) occur at night, but nighttime crashes account for half of fatal crashes. Furthermore, Minnesota experienced 70% of its fatal crashes in rural areas, as compared to 58% nationally. As a result, rural intersections at night are at higher risk for fatal crashes than other locations in Minnesota. This research evaluated the effectiveness of roadway lighting in reducing nighttime crashes at isolated rural intersections. A before-and-after study was used to evaluate the impact of lighting at 33 intersections with 3 years of before data and 3 years of after data. A 28% reduction in night crash frequency occurred after lighting was installed. A Poisson regression model evaluated the change in night crash rate after installation of lighting. Results indicated that the night crash rate was lower after lighting was installed and was statistically significant. The expected night crash rate before lighting was installed was 59% higher than after lighting was installed.

The site visits showed that at least 75% of the rural intersection street lighting was mounted on existing utility poles. Most of these lights would be considered destination lighting as they are not designed to specifically illuminate the intersection. This alternative does not require special installation of a light pole and provides a more cost-effective approach for the local agencies, but does not necessarily provide adequate lighting of the intersection.

  1. Carstens and Berns (1984), an evaluation of destination lighting was conducted in Iowa. Destination lighting is intended only to guide a driver to the intersection and may not provide sufficient lighting to increase visibility. This study found no significant differences in crashes between lighted and unlighted intersections on secondary roads. This research only considered destination lighting on low-volume roads where the volume ranges were not defined. It was unclear whether other studies included intersections with these characteristics.

  2. 3.

Effectiveness of Intersection Lighting, Cari Kinzenbaw (2007), Nighttime driving has proven to be particularly challenging. For example, the USDOT reports that 45% of all fatalities occur during dark conditions even though the miles driven during dark hours are considerable less than miles driven during light hours. Also, another study shows that the nighttime fatality rate is three times the daytime fatality rate. Crashes during dark conditions are more common than crashes during light conditions. In an effort to limit the dark conditions at intersections, roadway lighting may be installed. This strategy can be effective as long as the lighting levels and configuration allow the light to be useful. The purpose of this study was to determine the amount of light provided by particular types of lights and the different contours of light provided at certain distances away from the light at the intersection. By doing so, the actual placement of the lights may be adjusted in order to prevent specific types of crashes at certain intersections where they have proven to be significantly greater than other types of crashes.

  1. Standard and Nonstandard Roadway Lighting Compared with Darkness at Rural Intersections, Bruneau, Jean-Francois, Morin, Denis (2005), TRR 1918, This report evaluates the safety aspects of roadway lighting at rural and near-urban three-way and four-way junctions by comparing unlit intersections with those lit with two different types of lighting: (a) standard intersection lighting provided by the Ministère des Transports du Québec, Canada, and (b) nonstandard lighting provided by the local municipalities. A night-day accident rate ratio was used to estimate the accident rate reduction for three categories of severity: fatal and personal injury accidents, property damage only accidents, and all accidents. Sites were selected with two sampling modes. The objective mode selected sites according to the accident thresholds, and the arbitrary mode systematically selected all sites with standard lighting. The night-day accident rate ratio was measured for 376 sites by dividing the annual average number of accidents (6,546) with an annual average traffic flow (760 billion vehicles), calculated for both night and day. The accident rate reduction, expressed as a percentage, was tested for validity with the Student's t-test at the 5% p-level. The results were split into 49 categories with 20 variables to ensure that no significant variation existed in the accident rate reduction related to a specific roadway condition or environment. Rural lighting of an intersection significantly reduced the night accident rate by 29% for nonstandard lighting and by 39% for standard lighting, in comparison with darkness. When the two sampling modes were compared, standard lighting reduced the night accident rate of nonstandard lighting by 29%, significant at the 5% p-level, when only objective data in the sampling were used.

Tasks:

Specific tasks that will contribute to this final product include:

Task I: Data Collection and Analysis

  1. Field data collection at sites using road feature identification lighting (RFIL) and at sites with designed lighting (DL) systems in order to quantify the lighting characteristics at those sites. Preferably the sites will have similar geometric and other characteristics for comparison purposes.

  2. Crash data review for all sites being assessed.

  3. Analyze all data above to determine if there are any differences in crash experience (number, severity, rate, etc.) between sites with RFIL versus DL.

Task II: Development of Guidance and Recommendations

  1. Based on the analysis above, describe the benefits/disbenefits of both the RFIL and DL under different conditions.

  2. Identify situations in which RFIL is acceptable or unacceptable from a safety perspective.

  3. Identify “critical” roadway features that would either dictate a DL system or those that would allow RFIL.

  4. Provide guidance that can be used by practitioners when considering the use of RFIL – where and under what conditions it is acceptable.

  5. Provide recommendations on how roadway lighting standards could be changed to address the issue of RFIL application versus DL.

Implementation:

The result of the proposed research project will be considered for adoption by the Standing Committee on Geometric Design within AASHTO and for adoption by FHWA as program guidance for lighting of roadway features as to the number and placement of lighting luminaries for roadway features.

Sponsoring Committee:AKD10, Performance Effects on Geometric Design
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Patrick Hasson, National Safety and Design Team Leader, Federal Highway Administration
Source Info:TRB Standing Committees on Geometric Design, Operational Effects of Geometrics, and Visibility co-sponsored this research needs statement.
Date Posted:09/16/2010
Date Modified:03/17/2015
Index Terms:Highway design, Lighting, Lighting systems, Lighting columns, Intersections, Highway curves, Traffic accidents, Crash reduction factors,
Cosponsoring Committees:ACH40, Human Factors of Infrastructure Design and Operations
 
Subjects    
Highways
Design
Safety and Human Factors

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