Cable Median Barrier Systemic Review

May 2015

Table of Contents

1. Introduction ...... 2

2. Background ...... 2 2.1. Previous Efforts ...... 6 2.2. Completion of Cable Barrier ...... 7 2.3. Specifications and Construction Requirements ...... 7 2.4. Cable Barrier Maintenance ...... 8

3. Study Size ...... 10

4. Cross Median Collisions ...... 11

5. Implementation Approach ...... 13 5.1. Crash Modification Factors ...... 13 5.2. Estimated Benefits ...... 15 5.3. Estimated Costs ...... 17 5.4. Benefit-Cost Ratio ...... 18 5.5. Incremental Benefit-Cost Ratio ...... 19

6. Summary and Conclusions ...... 23

1. Introduction

Cross-median crashes often result in fatalities or serious injuries to occupants of the errant vehicle and the occupants of the vehicles traveling in the opposing lanes. The associated energy and speeds make these types of crashes particularly dangerous. Although the specific causes of cross median crashes (CMCs) may be difficult to determine, one method to reduce the severity and potential for these crashes is to install a median barrier. Cable barriers are more forgiving than concrete barriers and guardrail whereas several studies have shown a substantial reduction in fatal and injury crashes when compared to concrete and guardrail median barriers. Collision forces on cable barriers are deflected laterally reducing the forces transmitted to vehicle occupants. However, there have been problems reported including overrides, under- rides, shearing vehicle roof pillars, post fracture, and anchorage failures. Although the causes of these occurrences are not fully understood, possible factors that affect the effectiveness of cable barrier systems include the terrain geometry and shape, speeds and angles of the vehicles as they leave the road, lateral placement of the barrier, barrier system configuration (number and heights of cables), vehicle type (front geometry and mass), post spacing, and barrier lengths1.

The purpose of this systemic review is to perform a statewide analysis to determine the need and potential for cable median barriers along the interstate system in the State of Louisiana. The objective of this study is to identify candidate locations for cable median barrier installation and to develop a method for ranking median barrier improvements that would allow prioritizing them for funding.

2. Background

In order to provide guidance on the design and implementation of roadside safety hardware, including cable barriers, AASHTO began publishing the Roadside Design Guide (RDG) in 1989. The most recent edition was published in 2011 and has an entire chapter (i.e., Chapter Six) covering various types of median barriers including cable median barrier. According to the RDG, 80% of motorists departing the traveled way to the left (i.e., toward the median) could recover at or before a distance of 30 feet from where they departed. Thus, many designers felt installing median barriers in medians that were wider than this maximum recovery distance of 30 feet was unnecessary. However, increasing numbers of CMCs experienced by states in the 1990s changed this belief. In addition, there has been some discussion at the national level regarding an update to the recommended clear zone width. As a result, policies were put in

1 Marzougui, D., U. Mahadevaiah, F. Tahan, C. Kan, R. McGinnis, and R. Powers, “Guidance for the Selection, Use, and Maintenance of Cable Barrier Systems,” National Cooperative Highway Research Program (NCHRP), Report 711, Transportation Research Board, Washington, D.C, 2012.

This document and the information contained herein is prepared solely for the purpose of identifying, evaluating and planning safety improvements on public roads which may be implemented utilizing federal aid highway funds; and is therefore exempt from discovery or admission into evidence pursuant to 23 U.S.C. 409. 3

place by some states under which median barriers could be installed in medians up to 75 feet in width2.

Chapter Six of the RDG provides guidance on when to install a barrier. Information presented in the RDG gives guidance on whether a median barrier is recommended for installation, considered for installation, or could be optionally installed according to median width and average daily traffic (ADT). Specifically, median barriers are recommended when the median is less than 30 feet (10 meters) wide and ADT is greater than 20,000 vehicles per day (vpd). Barriers may be considered when median width is between 30 and 50 feet and ADT is greater than 20,000 vpd. Barriers are optional under the following criteria:

- Median width is less than 50 feet and ADT is less than 20,000 vpd; and - Median width is between 50 and 70 feet; ADT is not considered an influencing factor in this instance.

Non-tensioned cable barriers have been used for over 50 years on highway roadsides and medians. However, high tension cable barriers are a relatively recent technology implemented by highway agencies around the world, particularly in Europe and the US; and the published literature of the effects of these barriers is continuing to grow3.

One of the most comprehensive nationwide studies of the collision effects of median cable barriers reviewed experiences and performance of the barriers in 23 states4. The results of the analysis showed that there were significant reductions in CMCs for depressed medians with moderate slopes, but also noted that occasional penetrations of the barrier have occurred and the placement of the barrier demands improved procedures. Nine studies reported reductions in fatal CMCs ranging from 43% to 100%, with seven of them reporting over a 90% reduction. Five studies reported reductions in all severities of CMCs ranging from 52% to 96%, with four of them reporting over a 70% reduction. There were eleven studies that evaluated the number of penetrations as a measure of effectiveness. Six studies reported an effectiveness greater than 95% (that is less than 5% penetration rate), and only one study reported more than 10% penetration of the barrier. The study shows that cable barriers do result in more low cost property damage only (PDO) crashes (and the resulting need for barrier repairs), but that due to the relatively low cost of the barrier and the effectiveness in reducing severe crashes, the performance is generally deemed to be good across all studies.

Alluri et al. (2012)5 evaluated the safety performance of cable barriers on limited access facilities in Florida State from 2003 to 2010. Of all barrier crashes (i.e., involving vehicles hitting

2 American Association of State Highway and Transportation Officials (AASHTO), “Roadside Design Guide,” 4th Edition, AASHTO, Washington, DC, 2011. 3 Churchill, A. E., and M. Hassan, “High Tension Cable Barrier Performance Evaluation Study,” EBA Engineering Consultants Ltd. operating as EBA, A Tetra Tech Company, EBA File: E32101112.006, October, 2013. 4 Ray, M. H., C. Silvestri, C.E. Conron, and M. Mongiardini, “Experience with Cable Barriers in the United States: Design Standards, Policies, and Performance.” ASCE: Journal of Transportation Engineering, Vol. 135, No. 10, 2009, pp. 711-720. 5 Alluri, P., K. Hallem, and A. Gan. In-Service Performance Evaluation (ISPE) for G4 (1S) Type of Strong-Post W-Beam Guardrail System and Cable Median Barrier: Volume II. Florida DOT. December 2012.

a barrier) 16.4% were found to have crossed the barriers, and 83.6% were either contained or redirected by the barriers. The before-and-after analysis was based on only median-related crashes (i.e., involving vehicles leaving the travel lane toward the median). The results showed that cable median barrier installation reduced fatal crash rate by 42.2%, severe injury crash rate by 20.1%, and minor injury crash rate by 11.6%. Crash rates involving possible injury and property damage; however, increased by 53.1% and 88.1%, respectively, for an overall crash increase of 37.8%.

Sheikh et al. (2008)6 presented results of a survey from 27 states in relation to performance, design and construction, overall experience, and maintenance of cable barrier systems. The participating states identified the following factors as those that influenced their decision to install median cable barriers:

- Lower installation cost and a better benefit-cost ratio - Ease of repair after an impact - Ability of the high-tension system to retain some functionality after an impact - Better aesthetic and “see-through” appearance - Ability to allow lateral drainage

The participating states also reported that severity of crashes decreased at locations where cable barrier had been installed while the total number of crashes increased.

Agent and Pigman (2008)7 evaluated the effectiveness of Brifen TL-4 and Trynity CASS cable median barrier systems in preventing CMCs on specific sections of highways in Kentucky. About 325 hits with the cable barrier were reported on a 21-month period. However, only 185 hits involved a police report. The remaining hits involved a minor impact where the vehicle probably continued without filing a report. The results of the study show that the cable was successful in redirecting errant vehicles since in only 0.9% of the cases the cable system failed. It was also reported that the struck cable system could be repaired without major disruption to traffic.

North Carolina has been investigating CMCs since the early 1990s when this type of crashes began to be perceived as a problem on high-volume, high-speed, urban facilities. Hunter et al. (2001)8 estimated the effect of cable median barrier on crash rates by crash type. The study revealed that several types of crashes (especially run-off-the-road-left and fixed object crashes) increased after the installation of median cable barriers. However, there were fewer number of fatal and severe injury crashes. Moreover, Murphy (2006)9 conducted a long term median barrier evaluation. The study reported a significant reduction in the severity of total

6 Sheikh, D. L., D. C. Alberson, and L. S. Chatham, “State of the Practice of Cable Barrier Systems,” Transportation Research Record, Vol. 2060, No. 1, 2008, pp. 84-91. 7 Agent, K. R., and J. G. Pigman, Evaluation of Median Barrier Safety Issues, Report No. KTC-0814/SPR329-06-1F, Kentucky Transportation Center (University of Kentucky), Lexington, KY, 2008. 8 Hunter, W. W., J. R. Stewart, K. A. Eccles, H. F. Huang, F. M. Council, and D. L. Harkey, “Three-Strand Cable Median Barrier in North Carolina: In-Service Evaluation,” Transportation Research Record, Vol. 1743, No. 1, 2001, pp. 97-103. 9 Murphy, B. “Median Barriers in North Carolina-Long Term Evaluation,” Missouri Traffic and Safety Conference, 2006.

crashes, but an increase of total minor injury and PDO crashes. A few maintenance concerns were also identified including recovery of maintenance cost from drive-away vehicles, frequency of repairs to the cable barriers and mowing.

Arnold (2006)10 performed a three-year performance evaluation on the existing high- tension cable barrier system in Ohio. Even though crash frequency increased after installation, a significant number of possible CMCs were contained with zero fatal and severe injury CMCs reported.

Cooner et al. (2009)11 conducted a performance evaluation of cable median barrier systems in Texas. Assessment of the performance was based on 4 main elements including initial installation costs, routine maintenance and repair costs, before and after crash statistics and actual field performance during collisions. Relevant conclusions from the study included the following:

- Cable barriers were more cost-efficient (considering capital and life-cycle cost) than concrete median barriers - Cable barriers performed extremely well in most of the standard type collisions - Cable barriers are making a significant contribution to the reduction of fatal and severe injury crashes on state roadways, effectively eliminating 96% of these injury types caused by CMCs.

Washington State has been a pioneer in cable median barrier installations and their performance assessments. Glad et al. (2002)12 conducted a benefit-cost analysis to evaluate the cost effectiveness of median barrier installation on multiple divided highways with full access control. Cable barrier was found to be the most cost-effective where the median width was in the range of 30 to 60 ft. when compared to guardrail and concrete barrier. McClanahan et al. (2004)13 analyzed installation and maintenance costs of the median cable system by performing a before-and-after evaluation. The installation cost was estimated to be $44,000 per mile. The average cost of repair was found to be $733, and the average annual maintenance cost was approximately $2,570 per mile. Post installation, there was a significant reduction in the number of fatal and severe crashes. The study concluded that the annual societal benefits of cable barriers were approximately $420,000 per mile.

Hammond and Batiste (2008)14 evaluated the performance of cable barriers in Washington for the years 2000 to 2008. Analysis of across and within the median collisions

10 Arnold, E. T., Proprietary Tensioned Cable System: Results of a Three-Year In-Service Evaluation. Ohio Department of Transportation. 11 Cooner, S. A., Y. K. Rathod, D. C. Alberson, R. P. Bligh, S. E. Ranft, and D. Sun, Performance Evaluation of Cable Median Barrier Systems in Texas, Report No. FHWA-TX-09-0-5609-1, FHWA, U. S. Department of Transportation, 2009. 12 Glad R. W., R. B. Albin, D. M. McIntoch, and D. K. Olson. Median Treatment Study on Washington State Highways. Research Report Ward 516.1. Washington State Department of Transportation, Olympia, WA, 2002. 13 McClahan, D., R. B. Albin, and J. C. Milton, “Washington State Cable Median Barrier In-Service Study,” In Transportation Research Board 83rd Annual Meeting Compendium of Papers, Washington, D. C. 14 Hammond, P., J. R. Batiste, “Cable Median Barrier: Reassessment and Recommendations Update,” Washington State DOT and Washington State Patrol, 2008.

showed a reduction of 58% in fatal and severe injury crashes. When comparing the performance of cable median barriers with concrete barriers, 79% of errant vehicles were contained by cable median barriers while only 34% were contained by concrete median barriers.

Lastly, Olson et al. (2013)15 summarized the evolution and accomplishments of the Washington State Department of Transportation’s (WDOT) cable median barrier program of the previous efforts published in the “Cable Median Barrier Reassessment and Recommendations” reports of 2007, 2008, and 2009. The summary concluded that the program was successful on reducing the frequency and severity of CMCs on high-speed controlled-access roadways. The fatal collision rate was reduced from 0.26 per 100 mvmt to 0.13 per 100 mvmt. Due to the inherent low cost, the increased coverage combined with the effectiveness of cable barriers has offered a greater level of safety among Washington State. The researchers believe the cable median barrier program and its evolution in Washington State have met and exceeded the intent of the initial program for a low‐cost, safe, and effective median barrier system.

High-tension cable median barrier systems have increasingly been installed along limited or full controlled access facilities in a number of states. The general performance of cable barriers at redirecting or stopping vehicles has been found to be the most effective and economically efficient countermeasure for CMCs. Several before-and-after studies have found that cable barriers reduce fatal and severe injury crashes, even though they often result in an increase in total, PDO, and minor injury collisions.

2.1. Previous Efforts A multi-disciplinary Task Force Study including various Louisiana Department of Transportation and Development (LADOTD) sections, Louisiana State Police (LSP), Louisiana Highway Safety Commission (LHSC), and Federal Highway Administration (FHWA) was completed in April of 2007. The study evaluated median crossover crash data for the interstate system on a statewide basis to define any potential problem areas. The study recommended that in order to facilitate an effective and warranted appropriation of safety needs and safety funding across the state transportation system, policy decisions should be data driven and should take into account the implications to the remainder of the state roadway system if a barrier is warranted and installed. Therefore, data driven policy and criteria shall be applied to determine if any locations warrant the installation of a median barrier in Louisiana. In addition, a pilot program was recommended for installation of cable median barrier involving two locations:

- I-12, St. Tammany Parish (32 miles); and - I-10, St. James Parish (7 miles) which was incorporated into a scheduled overlay/rehab project.

15 Olson, D., M. Sujka, and B. Manchas. "Cable Median Barrier Program in Washington State." Report No. WA-RD 812.1. Olympia, WA. Jun. 2013.

Initial consideration of a crash threshold of 0.4 CMC/mile/year was established from input from peer states. These two locations had a cross median crash frequency of 0.39 crashes per mile and 0.58 crashes per mile, respectively.

A second crossover study of crash data was completed in October, 2010. This study was an analysis of 3 years of crash data; multiple years of crash data normalizes the data and addresses regression to the mean, thus providing a better indication of the crash patterns. As a result, additional locations were identified as candidates for installing cable median barrier:

- I-10, Jefferson Parish (2.5 miles), St. John Parish (8 miles), Ascension Parish (10 miles), East Baton Rouge Parish (1.2 miles); a total 22 miles of cable median barrier covering the entire corridor from New Orleans to Highland Road in East Baton Rouge parish; and - I-12, Tangipahoa Parish (19 miles including 0.5 miles in St. John from St. James parish line to the Hope Canal)

2.2. Completion of Cable Barrier As of August, 2014, 10 projects have been let and over 105 miles of cable median barriers have been installed according to the LADOTD Highway Program Projects. Table 1 shows a breakdown of all the projects involving cable barriers throughout the State. Information including project number, district, parish, dates, route, and control sections is also displayed in the table. As it is shown, six projects (white) were already completed and accepted. Those projects involved the 105 miles of cable barrier previously mentioned. In addition, four more projects (yellow) were let and are expected to be completed within the next two years covering 156 miles, and eight more (green) are expected to be let in the next two years involving almost 247 miles. All these projects will represent approximately 508 miles of roadway with cable median barrier throughout the State.

2.3. Specifications and Construction Requirements There are two main specifications related to the construction of cable median barriers in Louisiana: the NS Concrete Strip (03/13) and the NS Cable Barrier System (03/13). The cable systems sit on continuous concrete strips in accordance with the 2006 Louisiana Standard Specifications for Roads and Bridges. The strip is 5 inches thick and 3 feet wide centered along the cable barrier and reinforced with 6 x 6 – W 2.9 x W 2.9 welded wire fabric. The cable barrier consists of a four (4) cable pre-stretched, high tension cable barrier system, including concrete socketed line post foundations, concrete end anchors, gated end terminal treatments and any other appurtenances or hardware fittings in accordance with the requirements of the plans. The cable barrier system meets the NCHRP Report 350 Test Level 4 (TL-4) for system with 6H: 1V or flatter slope, or the NCHRP Report Test Level 3 (TL-3) system for 4H: 1V slope. The barrier uses a maximum post spacing of 16 feet center to center of post and is required to use an end anchor which provides for a separate end anchor connection for each cable and it is placed on a

minimum of 8 feet from the toe of slope for TL-4, and no further than 4 feet down a 4H: IV slope break point for TL-3.

2.4. Cable Barrier Maintenance Most maintenance costs associated with cable barriers result from crash damage. Since cable barriers are often placed where they can be hit frequently, these costs can be significant. In police-reported crashes, it is usually possible to get the offending driver’s insurance company to reimburse the State for these costs. However, since cable barriers are more forgiving, drivers often are able to drive away after a crash, which makes it difficult to collect from an insurance company. Data from a few states indicates that police reports are usually available for slightly more than half of the crashes. However, non-reported crashes are less severe, which means their repair costs will be lower16.

Cable barrier maintenance in the Louisiana is addressed independently by the Districts and reported to the DOTD Headquarters. Hits are generally reported by personnel, law enforcement agencies or the public. Repairs are performed either by District personnel or by a contractor. When maintenance involves a contract, the process is as follows:

1. Once a hit has been located, the Parish Maintenance Specialist, Parish Highway Maintenance Superintendent (PHMS), or their designee will: a. Assign a Hit Number b. Indicate Route and Direction, if applicable. c. Indicate Control Section. d. Indicate Mile Point, start and ending points, if applicable. e. Estimate the amount of damage to the cable barrier (i.e., number of posts, turnbuckles, length of damage, if applicable) f. Date of hit or discovery. 2. The Project Engineer assigned to manage the district’s participation shall be notified by email of the information listed above. 3. The Project Engineer will email the Contractor to authorize the repair. This action starts the time for calculating any stipulated damages. 4. The Contractor will inspect the damage within the time stated in the contract. If the repair involves 4 or more posts than estimated by the Specialist or PHMS, or a significant difference in any other item, the Contractor will contact the Specialist or PHMS to discuss. Otherwise, the Contractor is authorized to complete the repairs. Upon completion of the repairs, the Project Engineer is notified.

16 Marzougui, D., U. Mahadevaiah, F. Tahan, C. Kan, R. McGinnis, and R. Powers, “Guidance for the Selection, Use, and Maintenance of Cable Barrier Systems,” National Cooperative Highway Research Program (NCHRP), Report 711, Transportation Research Board, Washington, D.C, 2012.

Table 1 Cable Median Barrier Projects

Notice to Acceptance Route Control Log-mile Log-mile Segment Project District Parish Letting Date Proceed date Number Section From to Length H.003052 61 St. James 5/28/2008 8/28/2008 3/3/2009 I-10 450-12 0.00 6.84 6.84 450-13 0.00 5.15 5.15 H.003448 62 St. Tammany 5/28/2008 8/18/2008 12/2/2009 I-12 454-04 0.00 32.68 32.68 H.003059 62 Tangipahoa 8/25/2010 9/28/2010 10/18/2011 I-12 454-03 0.00 18.79 18.79 I-10 450-13 0.00 0.53 0.53 H.009013 61 E. Baton Rouge 6/15/2011 9/1/2011 12/17/2012 I-10 450-10 12.05 13.50 1.45 61 Ascension I-10 450-11 0.00 21.84 21.84 62 St. John Baptist I-10 450-13 0.53 12.78 12.25 2 Jefferson I-10 450-15 0.00 4.35 4.35 H.010071 2 Orleans 8/16/2012 12/5/2012 5/22/2013 I-610 450-34 0.51 0.78 0.27 I-10 450-90 10.27 10.71 0.44 H.010272 8 Vernon 6/12/2013 8/15/2013 3/3/2014 LA 8 373-01 6.73 7.36 0.63 H.010675 4 Bossier 7/10/2013 9/17/2013 NA I-20 451-02 0.00 18.56 18.56 Webster I-20 451-03 0.00 16.17 16.17 H.010684 4 Bienville 9/25/2013 2/01/2014 NA I-20 451-04 0.00 17.39 17.39 Caddo I-20 451-01 0.00 19.44 19.44 H.010685 5 Madison 10/23/2013 2/03/21014 NA I-20 451-08 0.00 32.88 32.88 Richland I-20 451-07 0.00 27.31 27.31 H.010712 2 Orleans 2/12/2014 6/20/2014 NA I-10 450-90 0.00 24.26 24.26 H.010911 5 Lincoln 10/08/2014 NA NA I-20 451-05 0.00 27.33 27.33 Ouachita NA NA I-20 451-06 0.00 28.57 28.57 H.010680 61 Iberville 1/13/2016 NA NA I-10 450-07 0.00 14.80 14.80 W. baton Rouge NA NA I-10 450-07 0.00 12.65 12.65 H.010683 62 Tangipahoa 10/14/2015 NA NA I-55 452-90 13.85 51.37 37.52 H.010865 7 Calcasieu 5/11/2016 NA NA I-210 450-30 0.00 12.68 12.68 H.010962 3 Acadia 3/09/2016 NA NA I-10 450-04 0.00 27.14 27.14 Lafayette NA NA 450-05 0.00 13.98 13.98 H.010864 7 Calcasieu 5/11/2016 NA NA I-10 450-91 9.60 27.50 17.90 Jefferson Davis NA NA I-10 450-03 0.00 22.36 22.36 H.011308 62 St. Tammany 2/14/2018 NA NA I-10 450-18 0.00 7.00 7.00 H.011278 62 Livingston 3/14/2018 NA NA I-12 454-02 0.00 25.78 25.78

5. The Project Engineer will notify the Specialist or PHMS that the repairs have been completed. The specialist or PHMS will inspect and verify that the work was done correctly. The Specialist or PHMS will email the Project Engineer that the work has been completed and is satisfactory. 6. Finally, the Project Engineer will notify the DOTD Headquarters.

As of July of 2014, a little over $380,000 has been spent towards cable median barrier maintenance accounting for both, personnel and contracts repairs since January 2014. Further evaluation of cable barrier maintenance costs is performed and explained in the following chapters.

3. Study Size

This cable median barrier study identified high-speed, controlled-access, rural, divided highway segments where there was no median barrier installed and the median width was greater than 10 feet. This includes segments that have projects scheduled from September, 2014 to 2018. Controlled-access highways were targeted because of the lack of left-turn movements across the median. Interrupting the barrier runs to provide for left-turning vehicles requires a more frequent need to terminate the median barriers and to provide adequate sight distance for turning vehicles. This would increase construction costs and make maintenance more difficult.

The study efforts produced a preliminary list of potential locations where median barrier would be considered for installation from the Surface-Type Log (STL) File (Highway Inventory) of the LADOTD Project and Highway Information. The list included the roadway geometrics and characteristics for every segment including control section, beginning log-mile, end log-mile, segment length, number of lanes, shoulder width, median type, median width, and AADT. The preliminary list was corrected and updated using the LADOTD Bing Map Tools together with the PMS Data (2012-2013) from the LADOTD Intranet by removing sections where median barriers (concrete or cable) were already installed, sections involving a tree line, or any other section were cable median barrier was not needed.

Table 2 shows several breakdowns of the 513.6 miles of the statewide controlled-access highway inventory where median cable barriers could be installed. The first table displays the number of miles separated by route and by district (potential projects). The second table shows the distribution of miles by route and the third table shows the distribution by district.

More than half of the miles that require cable median barriers correspond to mainly two routes (I-49 and I-10). District 8 (Alexandria) is the district with more miles to be covered, followed by District 62 (Hammond) and District 3 (Lafayette).

Table 2 Distribution of Statewide Controlled-Access Highway Miles for Cable Median Barrier Installation

Route District Length

I-10 3 37.2

I-10 7 39.4

I-10 61 32.9

I-10 62 12.7

I-12 62 18.2

I-20 5 53.4

I-210 7 10.6 Route Length

I-220 4 14.4 I-10 122.2

I-310 2 7.3 I-12 18.2

I-49 3 42.2 I-20 53.4

I-49 4 40.7 I-210 10.6

I-49 8 92.2 I-220 14.4 District Length

I-55 62 37.5 I-310 7.3 2 41.1

I-59 62 12.0 I-49 175.1 3 83.3

LA 3132 4 10.2 I-55 37.5 4 65.3

US 167 8 9.7 I-59 12.0 5 53.4

US 190 62 2.2 LA 3132 10.2 7 50.0

US 90 2 33.8 US 167 9.7 8 101.9

US 90 3 3.9 US 90 40.9 61 36.1

US 90 61 3.2 US 190 2.2 62 82.5 Total = 513.6 Total = 513.6 Total = 513.6

4. Cross Median Collisions

To analyze the history of cross-median crashes (CMCs) in the state of Louisiana, the cable median barrier study identified high-speed, controlled-access highway segments where cable median barrier is or could be installed. Crash data associated with those segments was downloaded on May, 2014 from the LADOTD Highway Crash List. The data set corresponded to all the crashes where the Prior Movement was “crossed median into opposite lane” (code E), or where the First, Second, Third, Fourth, or Most Harmful Event was “crossed median/centerline” (code L) for years 2009 to 2013. From the generated crash list, every crash report was downloaded from either Thinkstream or Content Manager (according to the investigating agency) and reviewed to verify whether the crash corresponded to a CMC. A final crash list was generated with only the crashes that corresponded to a CMC occurred within the study segments. Additional information associated with the crashes was also downloaded for further analysis including features like route number, district, parish, mile-point, control section, log- mile, and severity (fatal, severe, moderate, complaint and PDO).

Figure 1 displays the distribution of CMCs per year for the statewide controlled-access highways and the miles of cable barriers that have been installed from 2009 through 2013. It can be noted that since the beginning of the installation of cable barriers, the number of CMCs decreased from 169 to 114 per year.

200 120 169 165

100

148 150 132 80 114

100 60

50 Miles ofcable barrier CrossMedian Crashes 20

0 0 2009 2010 2011 2012 2013

Figure 1 CMCs for Statewide Controlled-Access Highways and Miles of Cable Median Barrier added per year

Figure 2 and Table 3 display the crash severity distribution of CMCs per year occurred within the statewide controlled-access highways. The number of fatalities was reduced from 17 to 8, severe injuries from 6 to 3, and moderate injuries from 37 to 17 per year since the installation of 105 miles of cable median barrier. This corresponds to a significant reduction, and 514.5 more miles are still to be covered.

Table 3 Crash Severity Distribution by year of CMCs for Statewide Controlled- Access Highways

Year TOTAL Fatal Severe Moderate Complaint PDO 2009 132 10 3 26 43 50 2010 169 17 6 37 48 61 2011 165 8 6 33 56 62 2012 148 8 2 18 54 66 2013 114 8 3 17 41 45 Average 145.6 10.2 4 26.2 48.4 56.8

200

145.6 150

100

56.8 48.4 NumberofCMCs 50 26.2 10.2 4 0 TOTAL Fatal Severe Moderate Complaint PDO

Figure 2 Crash Severity Distribution of Annual Average CMCs for Statewide Controlled-Access Highways 5. Implementation Approach

The purpose of this study is to perform a statewide analysis to determine the need and potential placement of cable median barriers along Controlled access facilities in the State of Louisiana, and to develop a method for ranking cable median barrier installations that would allow prioritizing them for funding. A benefit-cost ratio analysis was performed based on crash history of segments were cable median barrier had been installed, and an incremental benefit- cost ratio analysis was used for prioritizing. A detailed description of the tasks performed follows.

5.1. Crash Modification Factors To perform a benefit-cost analysis, it was necessary to identify the benefits expected from the installation of cable median barriers based on the estimated change in average crash frequency. A crash modification factor (CMF) is a value that quantifies the expected change in crash frequency at a site as a result of implementing a specific countermeasure or treatment. When selecting CMFs it is imperative to consider the evaluation study method used to develop the CMF, the quality of the CMF, and the applicability to the site of interest. The evaluation study design (i.e., how the study was conducted to calculate the CMF) plays a critical role in the quality of the CMF and should be considered when evaluating CMFs. Depending on the evaluation study design used to develop a CMF, the CMF could over or underestimate the effectiveness of a safety treatment.

Most agencies currently use the simple before-after study to estimate changes in crash frequency due to a specific change (safety treatment) at a site. However, this method does not account for regression to the mean or other changes (e.g., traffic volumes, weather, or driver

behavior) that may have impacted the site. The HSM presents methods for estimating changes in crash frequency using statistical methods that address these issues. The present study did not use these methods since they require the use of Safety Performance Functions (SPFs) which are not currently available for the type of roads analyzed in this study. This study, however, included AADT and segment length in the calculations of the CMFs as it is explained in this chapter.

As mentioned before, a total of 6 projects have been completed and over 105 miles of cable barrier have been placed in the State of Louisiana. Crash history for the segments where cable median barrier had been installed was extracted from the LADOTD Crash List (Crash 1 program). The data used for evaluation purposes corresponded to all non-intersection crashes (not only CMCs or median related crashes) that occurred within each segment three years prior to the start of construction (before period) and either three years after completion of the project or to December, 2013 when three years were not available (after period).

The number of crashes per year was calculated by severity (Fatal, serious, moderate, complaint, or PDO) for the before and after periods for every segment. A CMF was developed for every severity type dividing the number of crashes per year “after” by those “before” for each segment. In addition, to account for differences on AADT and length among the segments, a weighted mean of all segments was used to calculate the final CMFs considering both AADT and segment length as weights. Table 4 displays the final CMFs by severity with their corresponding weighted standard errors. It is worth mentioning that projects involving overlays, striping, pavement markings, and PCCP patching were also performed on some of the segments used to calculate the CMFs. Thus, the CMFs evaluated in this study should only be used as an estimate of the safety benefits expected by installing cable median barriers.

As shown in Table 4, installation of cable median barriers increased the total number of crashes that occurred within the segments by 10% (CMF = 1.10). However, the increase was caused by crashes related to property damage only (PDO), which corresponds to a CMF of 1.19. It is expected that the total number of crashes would increase after cable barrier installation since vehicles have less room to correct for roadway departure and could hit the barrier resulting in more PDO crashes. In terms of severity, cable median barriers reduced fatal and serious injury crashes by almost 30% and 20%, respectively. Moderate injury and complaint crashes were also reduced. As mentioned before, cable median barriers have reduced the number of CMCs in the state, which have been associated to high numbers of fatalities and serious injuries.

The CMFs calculated in this study are consistent to other cable median barrier studies where fatal and serious injury crashes decreased, but the total number of crashes increased after installation of cable median barriers17,18.

17 Churchill, A. E., and M. Hassan, “High Tension Cable Barrier Performance Evaluation Study,” EBA Engineering Consultants Ltd. operating as EBA, A Tetra Tech Company, EBA File: E32101112.006, October, 2013. 18 Ray, M. H., C. Silvestri, C.E. Conron, and M. Mongiardini, “Experience with Cable Barriers in the United States: Design Standards, Policies, and Performance.” ASCE: Journal of Transportation Engineering, Vol. 135, No. 10, 2009, pp. 711-720.

Table 4 Crash Modification Factors for Installation of Cable Median Barrier

Countermeasure: Install cable median barrier (high tension)

Crash Crash Roadway Area CMF SE CRF (%) Type Severity Type Type Principal 1.10 0.05 -10.46 All All Arterial Rural Interstate Principal 0.71 0.14 29.33 All Fatal Arterial Rural Interstate Principal 0.80 0.14 19.58 All Serious Arterial Rural Interstate Principal 0.82 0.10 18.01 All Moderate Arterial Rural Interstate Principal 0.95 0.05 5.12 All Complaint Arterial Rural Interstate Principal 1.19 0.05 -19.44 All PDO Arterial Rural Interstate

5.2. Estimated Benefits Crash data was downloaded from the LADOTD Crash List (years 2009 to 2013) for the updated list of segments identified as candidates for cable median barriers (Study Size chapter). The data used for evaluation corresponded to all non-intersection crashes (not only CMCs or median related crashes) that occurred within each segment. The average number of crashes per year by severity type was calculated for each segment and the reduction of expected crash frequency was estimated using the CMFs previously evaluated as follow:

Est. Crash Reduction = Avg. crashes per year - (Avg. crashes per year * CMF)

Converting the estimated change in crash frequency to monetary value is relatively simple as long as established societal crash costs by severity are available. First, the estimated crash frequency is converted to an annual monetary value. This monetary value may or may not be uniform throughout the service life of the project. Therefore, the annual value should be converted to a present value19.

19 AASHTO, “Highway Safety Manual”, AASHTO, 1st Edition: Volume 1, Washington, D.C, 2010.

Table 5 displays the Louisiana-specific cost of crashes based on the National Highway Traffic Safety Administration’s (NHTSA) “The Economic Impact of motor Vehicle Crashes, 2000” updated by the CPI.

Table 5 Louisiana-specific Cost of Crashes

Crash Type Average Cost

Fatal $1,270,370.00 Severe $938,791.00 Moderate $164,396.00 Complaint $8,141.00 PDO $3,292.00

These values were used to calculate the total annual monetary value of each segment as follow:

Total Annual Monetary Value = ∑

Where:

i = Fatal, Severe, Moderate, Complaint, or PDO crashes.

Then, the annual monetary values were converted to present values estimating a service life of 10 years and a minimum attractive rate of return of 4% using the following formula as described in the Highway Safety Manual (HSM) section 7.4.3.3 (Convert Uniform Annual Benefits to a Present Value):

PVbenefits = Total Annual Monetary Value * (P/A,i,y)

Where:

PVbenefits = Present value of the benefits for a specific segment,

(P/A,i,y) = Conversion factor for a series of uniform annual amounts to present value,

And:

(P/A,i,y) = ,

i = Minimum attractive rate of return or discount rate, and

y = Year in the service life of the countermeasure.

Finally, the total PVbenefit per project was calculated as the sum of the PVbenefit of the segments grouped by route and by district as shown in Table 6. Interstate I-10 displayed the

greatest PVbenefit within districts 61 and 3 with $33,995,145 and $27,855,616 respectively. These two projects also involved the greatest numbers of total crashes and were among the greatest numbers of fatalities and severe crashes per year among all the projects considered. The lowest

PVbenefit was estimated for a 3.2-mile segment located on US 90 and District 61. Only 14 crashes per year occurred within this segment in the last 5 years. The PVbenefit for all projects was estimated as $267,794,545.

5.3. Estimated Costs Estimating costs associated with implementing a countermeasure follows the same procedure as performing cost estimates for other construction or program implementation projects. Similar to other roadway improvement projects, expected project costs are unique to each site and to each proposed countermeasure(s)20.

The cost of implementing cable median barriers could include a variety of factors, e.g., construction material costs, grading and earth work, maintenance, and other costs including any planning and engineering design work conducted prior to construction. Calculating an estimated cost can be difficult because of the variability of these factors from site to site. Grading and earth work is probably the most variable and therefore most difficult to estimate. This study associated cable median barrier costs into two main categories: total construction costs and total maintenance costs.

Construction costs involve purchasing materials like cables, post, anchors, and other parts, together with the cost of site preparation and cable installation. An estimated construction cost of cable barriers was calculated from 10 projects that the DOTD has already let. The cost of every project was obtained from the LADOTD Highway Program Projects and was divided by the corresponding segment length. Only the portion related to cable median barriers was included in the estimate. The resulting estimated average construction cost of all projects in terms of dollars per mile is $136,400.47/Mile.

Maintenance costs include costs of parts, related labor, equipment rental, and mobilization and maintenance of traffic during repairs. The DOTD Maintenance Section (Section 42) provided two data sets to estimate the maintenance cost of cable median barriers. The data sets included the maintenance covered by the Districts (May of 2013 to June of 2014), and the maintenance given to contractors (November of 2013 to June of 2014) together with the expenses of every repair by date, cost, route and District. These values were associated by month and by segment with the information of the 6 cable barrier projects already completed to calculate an estimated annual maintenance cost per segment. In addition, to account for differences in length and AADT among all segments, the estimated annual maintenance cost was divided by both, the AADT and the length of each segment, respectively. The resulting

20 AASHTO, “Highway Safety Manual”, AASHTO, 1st Edition: Volume 1, Washington, D.C, 2010.

estimated average annual maintenance cost of the 6 projects in terms of dollars per year per mile per AADT is $0.21/Year/Mile/AADT.

A present value of the project cost was calculated for each segment of the updated list of candidates for cable median barrier (Study Size chapter). First, the estimated construction cost ($136,400.47/Mile) was multiplied by the length of each segment. Then, the estimated annual maintenance cost ($0.21/Year/Mile/AADT) was multiplied by the length and the AADT of each segment, and converted to present values. The present value of the project cost for each segment was determined as the sum of the construction cost and the present value of the maintenance cost as follow:

PVcost = (L * $136,400.47) + (L *AADT *$0.21) * (P/A,i,y)

Where:

PVcost = Present value of the project cost for a specific segment,

L = Segment length,

AADT = Segment annual average daily traffic,

(P/A,i,y) = Conversion factor for a series of uniform annual amounts to present value,

And:

(P/A,i,y) = ,

i = Minimum attractive rate of return or discount rate (4%), and

y = Year in the service life of the countermeasure (10 years).

Finally, the total PVcost per project was calculated as the sum of the PVcost of the segments grouped by route and by District as shown in Table 6. Interstate I-49 within District 8 corresponded to the project involving the longest distance. Since PVcost was highly associated to the length of the segment, I-49 within District 8 displayed the greatest PVcost ($14,824,840) due to its 92.2 miles. The lowest PVcost was estimated for the project located on US 90 within District 61, which did not necessarily involve the shortest distance since the AADT was also taken into consideration. The PVcost for all projects was estimated as $98,768,814.

5.4. Benefit-Cost Ratio A benefit-cost ratio (BCR) is the ratio of the present value benefits of the project to the implementation cost of the project. If the ratio is greater than 1.0, then the project is considered economically justified. The BCR was calculated using the PVbenefit and the PVcost associated by District by route (projects) previously evaluated as follow:

BCR =

Where:

BCR = Benefit-cost ratio for a specific project

PVbenefit = Present value of the project benefit for a specific district and route,

PVcost = Present value of the project cost for a specific district and route,

Table 6 displays the calculated BCR for all projects considered. As it is shown, only two projects were not found to be economically justifiable (BCR < 1.0). The projects involve 33.8 miles located on US 90 in District 02 (BCR = 0.51) and 92.2 miles located on I-49 in District 08 (BCR = 0.86). On the other hand, I-210 and I-220 were the two projects with greater BCR with values of 5.7 and 5.3, respectively. The BCR for all projects combined was estimated as 2.7. This represents that it would result economically justifiable to install cable barriers on all segments together. This would involve a present cost of $98,768,814, but a present benefit of $267,794,545.

5.5. Incremental Benefit-Cost Ratio The term “Ranking” in the Highway Safety Manual (HSM) refers to an ordered list of projects based on specific factors or project benefits and costs. Incremental benefit-cost (IBCR) analysis is an extension of the BCR. The ranking of the projects by IBCR analysis differs from the project ranking obtained with the cost-effectiveness and net present value computations. Incremental benefit-cost analysis provides greater insight into whether the expenditure presented by each increment of additional cost is economically justified1.

After performing the BCR evaluation for each project (segments grouped by route by district), projects with BCR greater than 1.0 were arranged in increasing order based on their estimated cost (the project with smallest cost was listed first). Beginning from the top of the list, the IBCR for the first two projects was calculated as follow:

( ) Incremental BCR =

Where:

PVbenefit 1 = Present value of benefit for lower-cost project,

PVbenefit 2 = Present value of benefit for greater-cost project,

PVcost 1 = Present value of cost for lower-cost project, and

PVcost 2 = Present value of cost for greater-cost project.

When the IBCR was greater than 1.0, the project with the higher cost was compared to the next project in the list. When the IBCR was lower than 1.0, the project with lower cost was compared to the next project in the list. This process was repeated and the project selected in the last pairing was considered the best economic investment. To produce the ranking of all projects, the entire evaluation was repeated without the project(s) previously selected until the ranking of every project was selected. This analysis was performed following the procedure described in the HSM section 8.2.1 (Ranking Procedures).

Table 6 shows the ranking of every project. As it is shown, the projects located on I-10 in Districts 03 and 61 were ranked first and second, respectively. Although these two projects had the greatest PVbenefits, neither of them had the greatest BCR. In addition, the last two ranks were given to the two projects that were not found to be economically justifiable (BRC < 1.0).

Figure 3 shows a comparison of the reduction in fatal crashes and miles of installed cable median barrier miles between the projects that the DOTD will let within the next two years and the proposed IBCR project ranking. Although the projects already planned will add miles of cable barrier faster, the proposed IBCR ranking will reduce fatalities sooner.

After finalizing the projects to be let in the next two years, 13 more projects will need to be scheduled and completed. The proposed list and rank of those projects is shown in Table 7. This study found that by continuing with the proposed ranking until completion of all projects, the number of fatal crashes among those segments are expected to be reduced from 50 to 35 per year. In addition, the State will have a total of 775 miles of cable barrier, which will also reduce the number of serious and moderate injuries enhancing safety among Louisiana’s high- speed, controlled-access roadways.

55 900

775 50 800 50

700

600

Continuing with IBCR ranking 500 Miles

40 Fatal Fatal Crashes

400

35 IBCR fatal crashes reduction 35 Scheduled fatal crashes reduction 300 IBCR miles addition 261 Scheduled miles additions 30 200 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Projects Figure 3 Planned Projects Vs. Proposed IBCR Ranking

Table 6 Benefits, Costs, BCR Analysis and IBCR Ranking of Projects

Fatal Severe Moderate Complaint PDO Total IBCR Scheduled Length Route District PV PV BCR Crashes Crashes Crashes Crashes Crashes Crashes Rank Rank (miles) benefits costs per year per year per year per year per year per year

1 2 I-10 61 32.9 $ 33,995,145 $ 7,917,684 4.29 7.4 3.6 32.6 135.2 389.6 568.4 2 NA I-49 3 42.2 $ 29,698,685 $ 8,029,132 3.70 5.2 4.4 36.2 118.8 322.2 486.8 3 5 I-10 3 37.2 $ 27,855,617 $ 8,066,463 3.45 4.4 5.8 29.2 94.0 273.6 407.0 4 1 I-20 5 53.4 $ 27,167,032 $ 10,655,234 2.55 5.0 4.0 32.0 112.6 380.2 533.8 5 3 I-55 62 37.5 $ 22,734,723 $ 6,722,227 3.38 6.2 1.4 11.8 77.0 228.0 324.4 6 6 I-10 7 39.4 $ 23,629,747 $ 8,514,787 2.78 4.4 4.0 23.4 100.6 306.6 439.0 7 NA I-220 4 14.4 $ 14,576,367 $ 2,756,778 5.29 1.6 3.8 19.6 52.8 156.2 234.0 8 4 I-210 7 10.6 $ 12,467,661 $ 2,191,455 5.69 2.2 2.2 14.4 67.0 220.8 306.6 9 8 I-12 62 18.2 $ 11,336,711 $ 3,694,482 3.07 1.4 2.4 16.8 38.4 122.8 181.8 10 7 I-10 62 7.3 $ 8,815,418 $ 1,833,128 4.81 2.6 0.4 5.4 35.4 203.2 247.0 11 NA LA 3132 4 10.2 $ 8,947,416 $ 2,165,895 4.13 0.8 3.0 11.0 40.0 138.8 193.6 12 NA I-59 62 12.0 $ 6,917,123 $ 2,357,242 2.93 1.4 0.8 7.2 19.0 57.8 86.2 13 NA I-49 4 40.7 $ 11,069,693 $ 6,948,578 1.59 2.0 2.2 9.4 31.2 119.0 163.8 14 NA US 167 8 9.7 $ 4,716,607 $ 1,759,509 2.68 0.6 0.8 8.4 26.2 76.2 112.2 15 NA I-310 2 7.3 $ 3,773,853 $ 1,539,786 2.45 1.0 0.2 3.0 18.4 63.4 86.0 16 NA US 190 62 2.2 $ 1,426,407 $ 496,855 2.87 0.4 0.2 0.6 10.0 49.8 61.0 17 NA I-10 62 5.3 $ 1,415,381 $ 1,104,039 1.28 0.4 0.0 1.6 11.0 41.4 54.4 18 NA US 90 3 3.9 $ 817,168 $ 697,825 1.17 0.0 0.2 2.4 4.8 14.2 21.6 19 NA US 90 61 3.2 $ 622,989 $ 572,145 1.09 0.2 0.0 0.2 4.8 8.8 14.0 20 NA I-49 8 92.2 $ 12,778,144 $ 14,824,840 0.86 2.4 1.2 18.0 64.6 155.2 241.4 21 NA US 90 2 33.8 $ 3,032,657 $ 5,920,730 0.51 0.6 0.2 6.0 53.8 135.2 195.8 Total = 513.6 $ 267,794,545 $ 98,768,814 2.71 50.2 40.8 289.2 1115.6 3463.0 4958.8

Table 7 Proposed Ranking for Future Projects

Fatal Severe Moderate Complaint PDO Total IBCR Length Route District PV PV BCR Crashes Crashes Crashes Crashes Crashes Crashes Rank (miles) benefits costs per year per year per year per year per year per year

1 I-49 3 42.2 $ 29,698,685 $ 8,029,132 3.70 5.2 4.4 36.2 118.8 322.2 486.8 2 I-220 4 14.4 $ 14,576,367 $ 2,756,778 5.29 1.6 3.8 19.6 52.8 156.2 234.0 3 LA 3132 4 10.2 $ 8,947,416 $ 2,165,895 4.13 0.8 3.0 11.0 40.0 138.8 193.6 4 I-59 62 12.0 $ 6,917,123 $ 2,357,242 2.93 1.4 0.8 7.2 19.0 57.8 86.2 5 I-49 4 40.7 $ 11,069,693 $ 6,948,578 1.59 2.0 2.2 9.4 31.2 119.0 163.8 6 US 167 8 9.7 $ 4,716,607 $ 1,759,509 2.68 0.6 0.8 8.4 26.2 76.2 112.2 7 I-310 2 7.3 $ 3,773,853 $ 1,539,786 2.45 1.0 0.2 3.0 18.4 63.4 86.0 8 US 190 62 3.1 $ 1,139,914 $ 694,279 1.64 0.2 0.4 4.2 47.8 237.2 289.8 9 I-10 62 5.3 $ 1,415,381 $ 1,104,039 1.28 0.4 0.0 1.6 11.0 41.4 54.4 10 US 90 3 3.9 $ 817,168 $ 697,825 1.17 0.0 0.2 2.4 4.8 14.2 21.6 11 US 90 61 3.2 $ 622,989 $ 572,145 1.09 0.2 0.0 0.2 4.8 8.8 14.0 12 I-49 8 92.2 $ 12,778,144 $ 14,824,840 0.86 2.4 1.2 18.0 64.6 155.2 241.4 13 US 90 2 33.8 $ 3,032,657 $ 5,920,730 0.51 0.6 0.2 6.0 53.8 135.2 195.8 Total = 277.1 $ 99,792,491 $ 49,173,354 2.03 16.6 17.0 123.6 455.4 1338.2 1950.8

6. Summary and Conclusions

High-tensioned cable barriers have increasingly been installed in the United States as a median barrier option, primarily as a result of state agencies looking for a cost-effective means by which to reduce or eliminate CMCs. While the general performance of cable barriers at redirecting or stopping vehicles has been found to be the most effective, several before-and- after studies claim that cable barriers reduce fatal and severe injury crashes, but increase total, PDO, and minor injury collisions. The cable median barrier used in Louisiana consists of a four (4) cable pre-stretched, high tension cable barrier system following the NS Concrete Strip (03/13) and the NS Cable Barrier System (03/13) specifications.

Cable barrier maintenance in the State of Louisiana is independently addressed by the Districts and reported to the DOTD Headquarters. As of July of this year, a little over $380,000 had been spent towards cable barrier maintenance accounting for both, personnel and contracts repairs, since January 2014.

In an effort to reduce the number of CMCs and their severity, the Louisiana DOTD has installed 105 miles of cable barriers throughout the State as of August, 2014. These few miles have reduced the number of CMCs from 169 to 114 per year among high-speed, controlled- access, rural, divided highway segments statewide. In addition, the number of fatalities was reduced from 17 to 8, severe injuries from 6 to 3, and moderate injuries from 37 to 17 per year for that same roadway classification. Four more projects will be completed in the next two years involving 156.01 miles on I-20 (Districts 04 and 05) and I-10 (District 02). Although these accomplishments are significant, the present study identified approximately 513.6 more miles of high-speed, controlled-access, rural, divided highway segments where cable median barrier installation would benefit the traveling public by enhancing safety.

The purpose of this study was to perform a statewide analysis to determine the feasibility and potential placement of cable median barriers and to develop a method for ranking cable barrier improvements that would allow prioritizing them for funding. The study identified high-speed, controlled-access, rural, divided highway segments where there was no median barrier installed and the median width was greater than 10 ft. These segments were then grouped by route by District (projects) and displayed in a table.

Crash modification factors (CMFs) were calculated for every severity type based on crash history of segments were cable barrier had previously been installed. The calculated CMFs were consistent to other studies where fatal and serious injury crashes decreased and total and PDO crashes increased after installation of cable median barrier. Projects involving overlays, striping, pavement markings, and PCCP patching were also performed on some of the segments used to calculate the CMFs. Thus, the CMFs evaluated in this study should only be used as an estimate of the crash modification expected by installing cable median barriers.

Present value benefits (PVbenefits) were estimated for every segment based on crash reductions calculated using the CMFs. A service life of 10 years and minimum attractive rate of return of 4% was also considered. When grouping the segments by route by district (projects)

Interstate I-10 displayed the greatest PVbenefit within Districts 61 and 03 with $33,995,145 and $27,855,616, respectively. By installing cable median barriers in all candidate segments identified in this study, the State could expect a PVbenefit of $267,794,545.

Cable median barrier costs were separated into two main categories: total construction cost and total maintenance cost. Construction costs were calculated as the average of 10 projects that have been already let ($136,400.47/Mile) and annual maintenance costs were calculated as the average maintenance cost of 6 completed projects ($0.21/Year/Mile/AADT).

From the construction costs and the annual maintenance costs, the PVcost was estimated for every segment for a service life of 10 years and a minimum attractive rate of return of 4%. When grouping the segments by route by District (projects), Interstate I-49 in District 08 displayed the greatest PVcost ($14,824,840), which was associated to having the greatest mileage (92.2 miles).

The PVcost for all projects together was estimated as $98,768,814.

Two out of 21 projects were not found to be economically justifiable through a benefit- cost ratio (BCR) analysis. The projects involve 33.8 miles located on US 90 in District 02 (BCR =

0.51) and 92.2 miles located on I-49 in District 08 (BCR = 0.86), which also had the greatest PVcost. The BCR for all the projects combined was estimated as 2.71, which represents that it would be economically justifiable to install cable median barriers in all candidate segments identified in this study. It should be noted that the BCR for these two segments would be greater than 1 if one fatality should occur. As a proactive approach, it is recommended to install the cable median barrier even if no fatalities have occurred. The potential for a fatality is greater without the presence of cable median barrier.

Finally, a ranking of all projects was determined through an incremental benefit-cost ratio analysis and it is presented in Table 6. This ranking can be incorporated into the decision making process for prioritizing cable barrier projects.

The DOTD has planned 8 new projects covering almost 237 miles that will be let in the next two years. These efforts will leave a remnant of approximately 277 more miles to be covered with cable median barriers. A ranking list of the projects needed to cover this remnant is proposed in this study (Table 7). This study concluded that by continuing with the proposed list until completion of all projects, the number of fatal crashes among the segments considered could be reduced from 50 to 35 per year. In addition, the State will have a total of 775 miles of cable barrier, which will also reduce the number of serious and moderate injuries increasing safety among Louisiana’s high-speed, controlled-access roadways.