Enhanced Delineation for Horizontal Curves

Enhanced delineation at horizontal curves includes a variety of potential strategies that can be implemented in advance of or within curves, in combination, or individually.

Potential strategies that can be implemented in advance of or within curves, in combination, or individually.
Potential Strategies	In advance of curve	Within curve
Pavement markings (standard width or wider)	X	X
In-lane curve warning pavement markings	X
Retroreflective strips on sign posts	X	X
Delineators		X
Chevron signs		X
Enhanced Conspicuity (larger, fluorescent, and/or retroreflective signs)	X	X
Dynamic curve warning signs (including speed radar feedback signs)	X
Sequential dynamic chevrons		X

Enhanced delineation treatments can alert drivers to upcoming curves, the direction and sharpness of the curve, and appropriate operating speed.

Agencies can take the following steps to implement enhanced delineation strategies:

Review signing practices and policies to ensure they comply with the Manual on Uniform Traffic Control Devices (MUTCD) principles of traffic control devices. Consistent practice for similar curves sets the appropriate driver expectancy.
Use the systemic approach to identify and treat problem curves. For example, Minnesota uses risk factors that include curve radii between 500 and 1,200 ft, traffic volumes between 500 and 1,000 vehicles per day, intersection in the curve, and presence of a visual trap.¹
Match the appropriate strategy to the identified problem(s), considering the full range of enhanced delineation treatments. Once the MUTCD requirements and recommendations have been met, an incremental approach is often beneficial to avoid excessive cost.

Photo: This photograph, taken from the side of the roadway, shows a two-lane undivided roadway bearing to the left. One the outside of the curve, to the right, is a clear grassy area least 20 feet in width, featuring a gentle foreslope and steeper backslope.

Chevron signs with retroreflective strips on sign posts installed along a curve.
Source: FHWA

Sources

1. Albin et al. Low-Cost Treatments for Horizontal Curve Safety 2016. FHWA-SA-15-084, (2016).

2. Srinivasan et al. Safety Evaluation of Improved Curve Delineation. FHWA-HRT-09-045, (2009).

3. Lyon et al. Safety Evaluation of Two Curve Warning Treatments: In-Lane Curve Warning Pavement Markings and Oversized Chevron Signs. Presented at the 96th TRB Annual Meeting, Paper No. 17-00432, (2017).

4. Hallmark, S. Evaluation of Sequential Dynamic Chevrons on Rural Two-lane Highways. FHWA, (2017).

5. Donnell et al. Reducing Roadway Departure Crashes at Horizontal Curve Sections on Two-lane Rural Highways. FHWA-SA-19-005, (2019).

Note: With the 2021 update of the PSCi, HFST is now included in Pavement Friction Management.

Safety Benefits:

Chevron Signs

25% reduction in
night-time crashes¹

16% reduction in non-intersection fatal and injury crashes²

Oversized Chevron Signs

15% reduction in fatal
and injury crashes³

Sequential Dynamic Chevrons

60% reduction in fatal
and injury crashes³

In-Lane Curve Warning Pavement Markings

35-38% reduction in all crashes.^4,5

New Fluorescent Curve Signs or Upgrade Existing Curve Signs to Fluorescent Sheeting

18% reduction in non-intersection, head-on, run-off-road, and sideswipe in rural areas.¹

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Page last modified on March 29, 2022