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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - Spring 2018

Spring 2018
Issue No:
Vol. 82 No. 1
Publication Number:
Table of Contents

Communication Product Updates

Communication Product Updates

by Lisa A. Shuler of FHWA's Office of Corporate Research, Technology, and Innovation Management

Below are brief descriptions of communications products recently developed by the Federal Highway Administration’s Office of Research, Development, and Technology. All of the reports are or will soon be available from the National Technical Information Service (NTIS). In some cases, limited copies of the communications products are available from FHWA’s Research and Technology (R&T) Product Distribution Center (PDC).

When ordering from NTIS, include the NTIS publication number (PB number) and the publication title. You also may visit the NTIS Web site at to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:

National Technical Information Service
5301 Shawnee Road
Alexandria, VA 22312
Telephone: 703–605–6050
Toll-free number: 1–888–584–8332 
Web site:

Requests for items available from the R&T Product Distribution Center should be addressed to:

R&T Product Distribution Center
Szanca Solutions/FHWA PDC
700 North 3rd Avenue
Altoona, PA 16601
Telephone: 814–239–1160
Fax: 814–239–2156

For more information on R&T communications products available from FHWA, visit FHWA’s Web site at, the FHWA Research Library at (or email, or the National Transportation Library at (or email


Behavior of a Steel Girder Bolted Splice Connection (Report)

Publication Number: FHWA-HRT-17-042


This report compares two design methods for bolted field splice connections on steel bridges. Using computer models, researchers created a hypothetical three-span steel bridge. They designed the connections using both a traditional method and a new method that makes conservative assumptions resulting in a simpler, streamlined procedure.

The researchers found that the design methods resulted in no difference in the numbers of bolts required for the flange splices. However, the models showed a significant difference in the number of bolts required for the web splices, with the new method requiring only two columns of bolts at a much larger spacing. Overall, the new method required 104 fewer bolts than the traditional method, making the connection more economical. The new method proved successful because it did not result in overstressing the girder or bolts at the strength limitstate.

Partly because of this work, in June 2016, the American Association of State Highway and Transportation Officials voted to adopt a new method for the design of bolted connections for steel bridges.

The document is available at


Advanced Methodology to Assess Riprap Rock Stability at Bridge Piers and Abutments (Report)

Publication Number: FHWA-HRT-17-054


Riprap is one of the most common materials used to protect bridge abutment and pier foundations from scour, or the removal of sediment by moving water. A key element of the design of riprap countermeasures is rock sizing, which is based on equations generally derived from simplified laboratory experiments. This report describes an advanced, numerical modeling procedure for analyzing the stability of riprap at bridge abutments and piers.

Researchers developed a new, advanced computational methodology for assessing the failure risk of geometrically complex riprap installations. They demonstrated that detailed fluid-structure interaction modeling can inform the evaluation of rock riprap movement for both the analysis of existing riprap aprons and for the design of new riprap aprons. The approach combined software for computational fluid dynamics and for computational structural mechanics.

Researchers computed the flow threshold for the onset of motion of a set of representative riprap rocks for both simplified laboratory and complex field conditions. They used physical laboratory experiments to validate the numerical procedures. Researchers also tested the methodology on a complex field case study of a riprap installation at a pier for a bridge over the Middle Fork of the Feather River in California. Although the case study application was successful, the approach is constrained by its high costs and limited availability. Consequently, good candidate applications for using the analysis to assess new or retrofit riprap installations are those with significant project costs or catastrophic failure risks.

This report also includes various recommendations for improving the design, installation, and monitoring of riprap apron installations at bridge piers and abutments, where feasible. Designers and engineers responsible for protecting bridge foundations will likely find this report useful.

The document is available at


Safety Evaluation of Edge Line Rumble Stripes (ELRSs) on Rural, Two-Lane Horizontal Curves (TechBrief)

Publication Number: FHWA-HRT-17-068


Several research studies have examined the use of shoulder rumble strips, but research into the performance of edge line rumble stripes (ELRSs) is rare. Rumble stripes are rumble strips created by placing edge line pavement markings over rumble strips. ELRSs are a variation of the common shoulder rumble strips used to alert drowsy or distracted drivers when they leave the travel lane to the right. Both target run-off-road crashes.

Shoulder rumble strips are located on the shoulder between the pavement marking and the outside edge of the pavement and are offset from the edge line pavement marking. In contrast, ELRSs are installed where the edge line pavement marking would normally be placed, and the pavement marking is installed directly over the rumble strip. In this way, the rumble stripes are closer to the travel lane than common shoulder rumble strips.

In addition, milled rumble strips generally are installed on roadway segments consisting of both horizontal tangents and horizontal curves. Installations on only horizontal curves are uncommon and, therefore, safety evaluations have not focused specifically on the effectiveness of horizontal curves. In addition, vertical faces are created within the milled rumble strip to which pavement markings are applied, thereby enhancing the visibility of the edge line during nighttime and wet-weather conditions.

This technical brief discusses research focused on the safety effectiveness of ELRSs on rural, two-lane horizontal curves in Kentucky and Ohio. Researchers aimed to estimate the safety effectiveness of ELRSs as measured by crash frequency. A further objective was to conduct a disaggregate analysis to investigate whether the safety effects vary by factors such as traffic volumes, the frequency of crashes before treatment, posted speed limit, and shoulder width. The evaluation of overall effectiveness included a benefit-cost ratio that considered the installation costs and crash savings.

The document is available at


Safety Evaluation of Red Light Indicator Lights (RLILs) at Intersections (Report)

Publication Number: FHWA-HRT-17-077


This report covers research conducted as part of FHWA’s Evaluation of Low-Cost Safety Improvements Pooled Fund Study. The document details a study that evaluated the safety effectiveness of red light indicator lights, which are auxiliary lights mounted on signal heads, mast arms, or poles directly connected to a traffic-control signal.

The red light indicator light activates at the onset of the red phase and enables an enforcement officer to observe red-light running from downstream of the intersection. This strategy is intended to reduce the frequency of crashes resulting from drivers disobeying traffic signals by providing a safer and more efficient means for police to enforce the red interval.

Researchers obtained geometric, traffic, and crash data at treated, four-legged signalized intersections in Florida. To account for potential selection bias and regression to the mean, they conducted an empirical before-after analysis using reference groups of untreated, four-legged signalized intersections with characteristics similar to those of the treated sites. The analysis also controlled for changes in traffic volumes over time and time trends in crash counts unrelated to the treatment.

Results indicate statistically significant crash reductions for most crash types, including disobeyed signal crashes, fatal and injury crashes, right-angle crashes, and left-turn crashes. Researchers estimated that the benefit-cost ratio with conservative cost and service life assumptions was 92:1 for four-legged signalized intersections. The results suggest that the treatment, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective.

In addition to the crash-related benefits, red light indicator lights can improve the efficiency and safety of enforcement of red-light running. Although the study did not evaluate the efficiency and safety impacts with respect to enforcement, it is important to recognize that red light indicator lights do enable police to observe violators from a downstream position, eliminating the need for a second observer (upstream) and the need to pursue a violator through the red light.

This report is available at