Material Requirements for High-Tension Cable Barriers: A Guide (2025)
Chapter: 3 Summary of the Survey of States
CHAPTER 3
Summary of the Survey of States
As part of the literature review, the research team reviewed the survey questionnaires from NCHRP Synthesis 493 and NCHRP Report 711. Overall, these surveys were aimed at collecting information from states on their use, selection, and placement criteria for high-tension cable barriers. Although this project benefited from the information collected and synthesized in the previous studies, the objective of this project was more focused on material properties, material testing, coating requirements, geotechnical testing, installation, and maintenance. Therefore, a survey was developed to address these topics, along with states’ standard specifications/details/provisions. The content of the survey distributed to the states included
- Twenty-five questions from NCHRP Synthesis 493. In some cases, it was necessary to edit the questions to add new information, or to improve comprehension;
- Five questions from NCHRP Report 711; and
- Eleven new questions that were designed to cover new content and were aimed at collecting material property, testing, and coating information.
The survey questions and the survey of state responses are provided as Appendices B and C, respectively.
A distribution list for the survey was assembled and included contacts from each of the 50 states. The survey was built using the online program SurveyMonkey, and the survey was opened for responses on October 21, 2022. Analysis of survey responses began on November 28, 2022.
The survey questions covered six general topics related to HTCB and are summarized in the sections below. The analysis of the survey results was then used to supplement the state DOT specifications and special provisions reviewed in the previous chapter of this report, which was developed with publicly available documents sourced by the research team.
Nineteen respondents, which represented 17 state agencies, initiated the survey. The Michigan DOT and Minnesota DOT were represented by multiple survey respondents. One additional state, Connecticut, responded to the survey by directly emailing the research team. A map indicating the states that responded is shown as Figure 6.
3.1 Systems and Features
The survey responses from transportation agencies revealed the following insights regarding the use and specifications for cable barrier systems:
- HTCBs are widely adopted, with 93% of respondents indicating their use within their respective states, while 21% also reported the use of low-tension cable systems.
- All HTCB systems and terminals (R350 or MASH) from various manufacturers were represented by at least one state among the survey respondents.
- The use of HTCB in median applications was unanimously reported, while 64% of respondents also indicated their use in roadside applications.
- When specifying the minimum number of cables, a majority (64%) required four cables, while 18% specified three cables. Notably, 18% of respondents did not stipulate a minimum number of cables.
- Regarding the minimum test level for HTCB, 63% of respondents required TL3, 18% specified TL4, and 18% did not have a minimum test level requirement.
These survey findings highlight the widespread adoption of HTCB systems across states, with variations in the specific requirements for the number of cables and minimum test levels. However, the use of HTCB in median applications appears to be a common practice among the surveyed transportation agencies.
3.2 State Specifications and Special Provisions
Respondents were asked whether their state had developed standard specifications for HTCB. The responses were evenly distributed, with roughly a quarter of participants selecting each available option, as illustrated in Table 25. Six respondents went on to provide files or links to their state’s standard specifications and/or drawings.
Regarding the development of special provisions for HTCB systems, the survey responses revealed a near-even split among the transportation agencies. Approximately half of the respondents indicated that their respective states had not developed HTCB special provisions, while the
Table 25. Tabulation of survey responses regarding standard specifications.
| Answer Choices | Responses | |
|---|---|---|
| Yes, specifications have been developed for each eligible system. | 17% | 2 |
| Yes, specifications have been developed but are not product specific. | 33% | 4 |
| No, use manufacturers specifications. | 25% | 3 |
| No. | 25% | 3 |
other half confirmed the development of such provisions applicable to all HTCB designs within their jurisdictions. Notably, five respondents provided files or links to their state’s specific special provisions for HTCB systems.
When queried about the methods employed to determine the warranting of cable barrier installations, the responses highlighted the following approaches:
- 45% of respondents reported using the AASHTO RDG as a reference.
- 64% of respondents indicated the use of agency-developed warrants or guidelines.
- 64% of respondents cited the consideration of crash history data in their warranting decisions.
These findings suggest that while some states have established dedicated special provisions for HTCB systems, others rely on general specifications or guidelines. Additionally, the warranting process for cable barrier implementation involves a combination of nationally recognized guidelines (e.g., the RDG), agency-specific warrants, and the evaluation of crash history data, with many agencies employing multiple criteria for their warranting decisions.
3.3 Materials
The survey inquired about various aspects related to materials used in HTCB systems. When asked if their agencies defined specific materials for HTCB components, the responses were evenly split, with half indicating the presence of such material specifications and the other half reporting no defined specifications.
Regarding material testing for HTCB projects, most respondents (67%) stated that they require the contractor or manufacturer to perform material testing and provide the corresponding certificates. One state mentioned conducting separate testing on a random sample of certain HTCB components.
When elaborating on material testing procedures, most states indicated that they require certificates for steel grade and galvanizing of cables, fittings, and posts when these tests are performed by contractors or manufacturers. As for agency-conducted testing, respondents mostly noted that concrete is typically tested in-house, unless specific circumstances necessitate the testing of steel reinforcing or coatings.
Concerning pull testing of fully fitted splices, most respondents (82%) reported that they do not require such testing. Additionally, most agencies (64%) specified the use of pre-stretched cable, while 36% reported using standard cable.
These findings highlight the varying practices among transportation agencies regarding material specifications, testing responsibilities, and specific testing requirements for HTCB systems. While some agencies have defined material specifications and rely on contractor or manufacturer testing, others conduct testing or have no defined specifications. The use of pre-stretched cable also appears to be more prevalent than standard cable among the surveyed agencies.
3.4 At- and Below-Grade Structures
Regarding anchor foundation design, most respondents (64%) indicated that the anchor foundations are designed by the manufacturer, 36% reported using a standard design, and none of the responding agencies indicated that they perform the anchor foundation design in-house. In contrast, 36% of the respondents indicated that their agency determines the placement and spacing of anchor foundations, while only one respondent (9%) indicated that the manufacturer determines placement and spacing. Many of the respondents indicated “Other,” typically indicating that anchor placement was performed on a project-by-project basis.
The respondents were asked if concrete line-post footers are designed based on the site-specific soil conditions. Half of the respondents indicated that local soil conditions were used and that the footer designs were performed by the manufacturers, while about a quarter of the respondents indicated that the agency performs the footer design. Most respondents (63%) indicated that mow strips are not used with HTCB, while approximately a quarter of the respondents indicated that they are used on all HTCB projects. Only one respondent indicated that mow strips are used on a project-by-project basis. The four respondents who indicated that mow strips are used by their agency indicated that either asphalt or concrete was used for the mow strip.
3.5 Design and Installation
When asked if HTCB systems affect site design, 73% of respondents stated that site design is independent of the system used. The remaining 27% indicated that site design is specific to the HTCB system being installed.
When asked about design modifications for curves (i.e., horizontal and vertical), about half of the respondents indicated that there is no specific design modification to account for curves. The other half indicated that there are specific design modifications for curves, with about half of those remaining respondents indicating that the design modifications are performed by the manufacturer, and the other half indicating it was done by the agency.
The respondents were asked how they transition from HTCB to more rigid (e.g., metal beam or concrete) barriers. The most common responses were that either the HTCB overlapped the more rigid barrier for some distance, or a gap was included between the two barriers so that they can operate independently of each other.
3.6 Maintenance, Repair, and Damage Modes
The survey respondents were asked if they had concerns with rusting and oxidation of HTCB components, most (80%) indicated that there were no concerns. The agencies were asked how frequently the cable tension is checked, the responses varied and are shown in Table 26.
The respondents were asked if anchor movement was monitored by their agency. Most (73%) indicated that anchor movement is not monitored, while 18% indicated that movement is monitored after installation and periodically thereafter. The survey respondents were asked to identify HTCB failure modes that they had encountered. The most common failure modes were end-anchor pull-out because of soil conditions (45%), post footer pull-out because of soil conditions (45%), followed by post failure because of post-sleeve concrete failure (27%), and failure at the end of cable connections.
The survey participants were asked to identify any challenges that they had faced with HTCB. Most respondents indicated challenges related to installation and soil conditions, one respondent indicated a lack of training, and another cited cost as a challenge.
Table 26. Tabulation of survey responses regarding cable tension check frequency.
| Answer Choices | Responses | |
|---|---|---|
| After installation | 45% | 5 |
| Every 6 months | 9% | 1 |
| Every year | 18% | 2 |
| Every 2 years | 9% | 1 |
| After minor repairs | 64% | 7 |
| After major repairs | 73% | 8 |
| Other (please specify) | 9% | 1 |
In the concluding section of the survey, respondents were asked whether their respective agencies had ISPEs of HTCB systems. The responses revealed that only two states, Wisconsin and Florida, representing 18% of the survey participants, reported having performed such evaluations. The remaining respondents indicated that their agencies had not undertaken ISPEs specifically focused on HTCB systems. This finding suggests that while the implementation of HTCB systems is widespread among transportation agencies, comprehensive assessments of their in-service performance appear to be limited. The lack of extensive ISPE data on HTCB systems may represent an opportunity for further research and analysis to gain insights into the real-world performance and potential areas for improvement in the design, installation, and maintenance of these barrier systems.
