Frequently Asked Questions

1. Can roadside terminals be used on a left shoulder if shoulder is a median for oncoming traffic?
2. What are the recommended grading details in front of and behind the terminals?
3. Can a terminal be used at a steep slope?
4. When a terminal is installed on a steep grade, what is the proper placement of the impact head?
5. Can terminals be used on a curve?
6. Does the FLEAT terminal need to have additional flare if the run of guardrail is already flared?
7. Is a special attachment required to connect the last FLEAT rail section to the beginning of the run of guardrail where the straight flare begins?
8. Can 6’-0” long steel foundation tubes without soil plates be used at SKT posts #3 through #8?
9. Can breakaway steel posts be mixed with breakaway wood posts in the same terminal?
10. Can breakaway steel posts be mixed with breakaway wood posts in the same terminal?
11. Can standard hex bolts be used to attach the cable anchor bracket to the guardrail end section?
12. Can the SKT, FLEAT or FLEAT-MT be supplied in weathering steel such as Corten?

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1. Q: Can roadside terminals be used on a left shoulder if shoulder is a median for oncoming traffic?
   
   A: 

   Yes, provided the distance from the exit slot of the terminal to the edge of the pavement for the oncoming traffic is at least 20 feet. Studies of many accidents have shown that a lateral distance of 20 feet was the effective maximum distance that any component of a damaged tangent terminal came to rest. The recommended 25-foot distance has a 5-foot safety factor.

   
   
   
2. Q: What are the recommended grading details in front of and behind the terminals?
   
   A: Special grading is required around guardrail terminals to assure that field performance is similar to that observed during full scale crash testing. Note that crash testing is normally conducted on flat ground and it is important to avoid installing terminals on or too near steep slopes. Relatively flat terrain is required in front of guardrail terminals in order to assure that vehicles are not vaulted into the air or diving into the ground when the terminal is struck. Further, modest slopes are utilized behind guardrail terminals in order to allow sufficient recovery areas for vehicles gating through the end treatment. The FHWA has developed guideline requirements based on engineering judgment for both tangent and flared terminals. See FHWA Memo “Site Grading Details for Selected Guardrail Terminals” dated May 22, 1996 and FHWA Technical Advisory T5040.33 “Corrugated Steel Guardrail Terminals” dated February 9, 1993 for additional information. Generally, energy absorbing terminals (such as the SKT & FLEAT) would require less stringent grading requirements than pure controlled gating terminals. Ongoing additional research is needed to give better guidelines.
   
   
   
3. Q: Can a terminal be used at a steep slope?
   
   A: Remember that a terminal does not solve a slope problem. If there is a steep slope in the immediate vicinity of the terminal, additional barrier may be needed before the terminal is installed. See the question above on grading for additional information.
   
   
   
4. Q: When a terminal is installed on a steep grade, what is the proper placement of the impact head?
   
   A: The important thing to remember is to keep the impact head parallel to the guardrail, not perpendicular to post #1. The reason is to allow the head to freely travel down the rail. The SKT & FLEAT impact heads are connected to the first post of the terminal with either two lag screws 3" long (for a wood post) or two hex head bolts 4" long (for a steel post). When the system is impacted end-on, the impact head only needs to move a short distance before the first post is fractured. The connection of the impact head to the post needs to be strong enough to support the weight of the head prior to impact. If the terminal is placed on a hill and the posts are driven so they will not be perpendicular to the guardrail, the post bracket angle on the impact head will not set flush against the post. Normally that gap will not exceed a width that will prevent the lag screw or hex bolt from holding the impact head to the post. If under extreme circumstances the gap becomes too large and the connection is not secure, we would recommend using a longer bolt.
   
   
5. Q: Can terminals be used on a curve?
   
   A: The SKT & FLEAT terminals themselves cannot be curved. In order for the impact heads to travel down the rail during end-on impacts, the rail must be straight to maintain the column strength of the rail section. The last downstream rail section of the terminal may be bolted to the beginning of the first curved guardrail section.
   
   
6. Q: Does the FLEAT terminal need to have additional flare if the run of guardrail is already flared?
   
   A: When the FLEAT is attached to a run of guardrail that is parallel to the travelway, the offset flare for the FLEAT is measured from the point where the guardrail ends and the FLEAT begins. The offset for the FLEAT can be varied anywhere between 2'-6" to 4'-0" (3.8 degrees to 6.1 degrees) over the 37'-6" long terminal length. These offsets represent flare rates of 15:1 to approximately 10:1. When the FLEAT is attached to guardrail that has been flared per the recommendations of the AASHTO Roadside Design Guide, the flare rate for the FLEAT may not need to be changed from that of the downstream guardrail. If the flare rate of the guardrail falls between 15:1 and 10:1, install the FLEAT in line with the run of guardrail at the same flare rate. If the flare rate of the guardrail is less the 15:1, then you must adjust the FLEAT farther away from the run of guardrail to provide the proper flare rate. If the recommendations of the AASHTO Roadside Design Guide are followed, the standard run of guardrail will not have a flare rate that is greater than 10:1 (semi-rigid barriers) for Test Level 2 (70 km/hr) or Test Level 3 (100 km/hr) design speeds. This means the FLEAT should not need to be flared back toward the travelway with respect to the flare rate of the guardrail.
   
   
7. Q: Is a special attachment required to connect the last FLEAT rail section to the beginning of the run of guardrail where the straight flare begins?
   
   A: No. The contractor must install the FLEAT beginning at the downstream end where the run of guardrail begins and work toward post #1. The splice of the last FLEAT rail section where the flare departure begins (FLEAT post #7 for the 37’-6” long Test Level 3 system) must be firmly bolted before the rail within the FLEAT itself is flared. If desired, post #7 can be set back a short distance to minimize the severity of the bend at that post. The angle of departure will depend on the offset selected. Based on a Test Level 3 FLEAT that is 37'-6" long, the maximum angle will be 6.1 degrees for a 4'-0" offset and the minimum angle will be 3.8 degrees for a 2'-6" offset. For a Test Level 2 FLEAT, the angle will remain the same but the offset will change to 2'-8" and 1'-8" respectively.
   
   
8. Q: Can 6’-0” long steel foundation tubes without soil plates be used at SKT posts #3 through #8?
   
   A: No. The 6’-0” long steel foundation tubes without soil plates may only be used at SKT posts #1 and #2. If foundation tubes and soil plates are used at SKT posts #3 and #4 or at #3 through #8, they must be either the 4’-6” or 5’-0” long foundation tubes. The soil plates for these short tubes at posts 3 - 8 are now optional. The 4’-6” or 5’-0” long foundation tubes with soil plates may also be used at SKT post #1 and #2 if desired. Either way, steel foundation tubes must be used at posts #1 and #2 for the wood post option.
   
   
9. Q: Can breakaway steel posts be mixed with breakaway wood posts in the same terminal?
   
   A: Yes. The thing that is important to remember is the foundation tube criteria as described in the above two questions. With the exception of a few nuts and bolts and the wood blocks (routed blocks needed for the steel posts), all of the SKT and FLEAT components are interchangeable between the wood post and the steel post options.
   
   
10. Q: Can breakaway steel posts be mixed with breakaway wood posts in the same terminal?
    
    A: Yes. The thing that is important to remember is the front anchor criteria
    as described in the Steel Post Installation Manual. With the exception of a
    few nuts and bolts and the wood blocks (routed blocks needed for the steel
    posts), all of the SKT and FLEAT components are interchangeable between the
    wood post and the steel post options.
    
    
11. Q: Can standard hex bolts be used to attach the cable anchor bracket to the guardrail end section?
    
    A: NO!! The anchor bracket for the SKT, FLEAT and FLEAT-MT require eight
    special 1/2" high strength cable anchor bracket shoulder bolts with two
    structural washers and a 1/2" structural nut. The unthreaded shoulders of
    the bolts provide the release mechanism for the anchor bracket for end-on
    impacts.
    
    
12. Q: Can the SKT, FLEAT or FLEAT-MT be supplied in weathering steel such as Corten?
    
    A: The guardrail sections may be weathering steel but the impact heads may
    not. The reason is the impact heads are fabricated from high strength steel
    and we must maintain those material properties. We can however paint the
    impact head brown after it is hot dipped galvanized to match the weathering
    steel.
    
    

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