Development of Guidance for Enhanced Delineation of Barriers and other Roadside Safety Hardware, Slopes, and Hazards
safety hardware is crash tested to assess the crashworthiness of the device.
The current crash test criteria are contained in the AASHTO Manual for
Assessing Safety Hardware (MASH) and all transportation agencies are in the
process of implementing MASH hardware on their highway systems.
However, like all hardware assessment, MASH testing is conducted within the
sterile, idealized environment of a laboratory test deck, and does not encompass
human factors regarding perceived danger and consequent driver behavior to
specific delineation practices of safety barriers or other roadside hazards.
Transportation agencies have encountered
situations where enhanced continuous delineation of the face of existing
roadside barriers seem to be playing a significant role in the reduction of
crashes and injury severity. Examples of such situations could be related to
the reduction of motorcycle impacts at strategic locations where a metal rub-rail
was added to the guardrail system and painted yellow. Similar crash reductions
were noticed when the yellow colored DR-46 motorcycle attenuator rub-rail was
added to existing guardrail systems.
This research will develop guidance for enhanced delineation of roadside barriers and other hazards such as steep slopes in order to provide increased visibility and improved safety performance. Such guidance will also address delineation applications for reducing vehicle interaction with pedestrians and bikes on multi-modal roadways.
The guidance developed through this research directly correlates with TCRS’s Strategic Plan and the number one goal in the TCRS mission statement which is, “develop, implement, and maintain guidance which will reduce fatal and incapacitating-injury roadway departure crashes.”
Based on before and after crash studies
conducted by multiple states, there appears to be a strong correlation between
enhanced longitudinal delineation measures and crash and injury reductions.
Thus, there is an urgent need to explore this topic further with the goal of developing
new delineation guidelines and procedures that would assist transportation
agencies in the application and implementation of delineation strategies for roadside
barriers, steep slopes, multimodal facilities, etc. Potential benefits include improving the
safety of roadways through effective delineation practices as well as
decreasing the potential for tort liability for transportation agencies.
Another potential benefit of this guidance would be increased exposure of
effective delineation methods available to agencies. As delineation methods
tend to be lower cost strategies, these solutions are likely to be more readily
and widely implemented by transportation agencies resulting in a potentially
far-reaching effect on reducing crashes and injuries.
At the recent
AKD20 Roadside Safety Conference, Utah DOT noted that their installations of a yellow powder coated metal motorcycle
rub-rail under a standard w-beam guardrail on two state maintained routes
resulted in a significant reduction in motorcycle crashes and injuries.
California Department of Transportation (CalTrans) installed the yellow colored
DR-46 Motorcycle Attenuator rub-rail in a curve on one of their state primary
routes experiencing a high number of motorcycle crashes and in the after
evaluation period, the number of motorcycle crashes in the subject curve reduced to zero. CalTrans and UDOT Engineers theorize that the
yellow color may have played a significant role in the reduction of motorcycle
crashes. Similarly, North Carolina DOT’s experience with the yellow DR-46
installed on NCDOT highways shows promise in reducing motorcycle crashes,
although it is early in the evaluation phase of the project. While all these examples are
specific to motorcycle crashes, improved/enhanced delineation may have the
potential to reduce crashes with other vehicle types as well.
transportation agencies often encounter situations where enhanced delineation
of existing safety barriers and steep slopes could likely contribute in the
reduction of vehicle crashes and severe injuries, there is no specific
documentation of proper practices and their effectiveness in mitigating these
problems. Neither are guidelines
available on how transportation agencies should address these situations. Irrespective of this perceived lack of
resources, a literature search should be conducted to identify to the extent
possible, best practices in the field and any published studies that might
provide insight into the effectiveness of delineation practices. There were a
small number of studies conducted in the late 1980’s examining delineation
practices specific to crash cushions (see below) that may provide a starting
point but other studies may exist.
· Lerner ND,
Turner BK. Laboratory Evaluation of Crash Cushion Delineation. Transportation
Research Record 1093: 1986.
· Creasey FT,
Dudek CL, Huchingson RD. Evaluation of the Effectiveness of Crash Cushion
Delineation. Transportation Research Record 1111: 1987
· Torbic, D.J.
et al. Guidance for Implementation of the AASHTO Strategic Highway Safety Plan.
Volume 7: A Guide for Reducing Collisions on Horizontal Curves. NCHRP Report
500, Transportation Research Board, Washington DC, 2004.
The anticipated tasks of this research are:
Identify best practices of
enhanced delineation of roadside barriers and steep slopes, as currently
adopted by transportation agencies.
Identify the effectiveness
of such delineating practices, as reported by existing transportation agencies
Develop guidance that
agencies can apply to delineate roadside hardware systems, slopes, and
multi-modal facilities adjacent to roadways.
Propose any needed updates of
appropriate sections of the AASHTO Roadside Design Guide (RDG) and the Manual
on Uniform Traffic Control Devices Recommended (MUTCD), and the AASHTO MASH
The result of this research project
will provide guidance to assist state and local transportation agencies in
determining enhanced practice solutions for delineating roadside safety barriers
and steep slopes. Such guidance will also support effective delineation
practices to limit the interaction between vehicles and vulnerable users for
multimodal pedestrian /bicycles facilities.
The guidance could be further implemented through
an update of appropriate sections of the AASHTO RDG, MUTCD and MASH.
Results of this research and the resulting guidance will be disseminated to state DOT design engineers, state and local traffic safety engineers, engineering consultants, and practitioners through presentations and webinars at appropriate industry and professional meetings including TRB Roadside Safety Design Committee, AASHTO TCRS, and Committee on Bridges and Structures Technical Committee T-7 “Guardrails and Bridge Rails.”
List the AASHTO Committee(s) and/or Council(s) – and any other organization – that might be interested in the research results and could help support implementation.
AASHTO, Technical Committee on Roadside Safety _ D. D. “Bucky” Galloway, TCRS
AASHTO, Committee on Bridges and Structures Technical Committee T-7, Alex Bardow, TCRS
AASHTO, Committee on Traffic Engineering
AASHTO, Committee on Safety
|Sponsoring Committee:||AKD20, Roadside Safety Design
|Research Period:||24 - 36 months|
|RNS Developer:||Chiara Silvestri Dobrovolny, Douglas J Gabauer, Richard Butler, D. D. “Bucky” Galloway|
|Source Info:||AKD20 Summer Meeting 2020|
|Index Terms:||Crashworthiness, Barriers (Roads), Roadside hazards, Roadside structures, Slopes, Highway safety, Design methods, Guardrails, |
Safety and Human Factors
Bridges and other structures