Memorandum 

SENT VIA ELECTRONIC MAil 

S\Jbject: AaION: Supplementary Guidance for the Selection afW-8eam Barrier Dale" 

Terminals 

,,'-' J 1 

Fr~~~~{F- ,jU£-"'Oirector, Office of Safety Design "'" Am.at . HSA-iO 

~: Safely Field 

My OClober 26, 2004, memorandum, "Guidance for the Selection ofW-beam Tenninals", 

transmitted detailed information intended for use by roadway designers as an aid in selel;ting the 

most appropriate \V-beam terminal for a specific site. The guidelines presented therein are 

currcmly being reviewed by members of the AASHTQ Technical Comminee for Roadside 

Safely for inclusion in the next edition oflhe AASHTO Roadside Design Guide (ROG). In the 

meantime, some have expressed a concern that the federal guidelines are misleading in regard \0 

the runout areas needed behind and beyond gating terminals. This memorandum provides 

additional information to assist designers in making appropriate barrier terminal selections. 

Current terminal selection recommendations, both in the FHWA Guidelines and in the 2002 

RDG, call for a minimum distance of 75' ~ 20' adjacent to the backside of the \V-beam 

immediately downstream from thc terminal end. This distance is clearly noted as being a 

minimum distance based on the final resting position of the 1800-lb small car in several W-beam 

terminal end-on tests (NCHRP Repon 350 test 3-30). Given the greater weight and resultant 

impact severity of the 4400-!b pickup truck, it is obvious that a greater nmout area would be 

needed for the truck impact at the same speed and angle (test 3-31). Several individual 

acceptance letters have specifically noted the distance traveled by the pickup truck in the 

certification tests and have recommended a minimum length of barrier to accommodate the 

observed post-crash trajectory. 

To assist the designer in selecting an appropriate terminal at a specific site, I am attaching both a 

tabular and a graphic summary showing the distances traveled and the reponed resting positions 

of both types of test vehicles in selected certification tests. These test data show the reponed 

resting positions of both the small car and the pickup truck after impacts into energy-absorbing 

designs (BEST, ET-series, SKT, and FLEAT) and non-energy absorbing designs (REGENT, 

SRT). As would be expected, in the end-on tests (3-30 and 3-31) the impacting vehicles traveled 

m!FUP 

.l!-~. ERICA 
a greater distance behind the barrier after striking non-energy absorbing terminals. Also as 

expected, terminal type has linle affect on a vehicle's post-crash travel distance when impacted 

at an angle (tests 3-32 and 3-33) because energy-absorbing terminals arc most effective in 

limiting penetration behind the barrier in head-on crashes. Finally, as noted above, bigher 

weight vehicles traveled further distances after impact. 

The selection of an appropriate \V-beam tenninal must be a deliberate choice based on specific 

sile conditions. At locations where: 

• flat angle impacts an: possible and the terrain behind and adjacent to the barrier could 

aHowa vchide \0 reach the shielded haz.vd, or 

• where the terrain behind and adjacent \0 the barrier in advance of the primary (shielded) 

area of concern is itself likely to cause serious occupant injuries in a crash, 

2 

either the barrier itself should be Imgtltmed to lessen the likelihood !hat a vehicle behind the 

rail will reach the primary (or any secondary) filled object or non-traversable terrain, or an 

enagy-absorbillg lermillal sltauld be cOllsidered. Even in the lauer instance, the recommended 

minimum ronout area should be provided wherever practical. 

Please discuss barrier tenninal selection procedures with those in the State DOT responsible for 

this activity to ensure they are aware of current guidelines and are taking them into consideration 

in their terminal selection and installation decisions. States not already doing so should also be 

asked to investigate all fatal crashes involving barrier tenninals 10 determine if the barrier length 

or terminal type/location may have contributed to the crash severity. In-service performance 

evaluation ofall safety appurtenances is the only means available to verify the assumed 

crashworthiness of safety hardware based on limited certification tests and to identify unforeseen 

problems with hardware that need to be addressed. 

Attachment 
Full Scale Crash Test Results for W-Beam Term

(Final Resting Position of Vehicle Shown for TL-3 Impact Conditi

System 

Type / Name 

Test 3-30 

820kg / 0 deg / offset W/4 

Test 3-31 

2000kg / 0 deg / centered 

Test 3-32 

820kg / 15 deg / centered 

200

Tangent 

BEST 

Energy Absorbing 

Lat. 8.8 m (28.9 ft) 

Long. 17.1 m (56.1 ft) 

Lat. 0.9 m (3.0 ft) 

Long. 8.9 m (29.2 ft) 

Lat. 13.2 m (43.3 ft) 

Long. 21.7 m (71.2 ft) 

L

L

Lat. 2.0 m (6.6 ft) 

Long. 7.62 m (25.0 ft) Tangent ET 2000 

Energy Absorbing 

Lat. 1.7 m (5.6 ft) 

Long. 6.3 m (20.7 ft) Lat. 0.0 m (0.0 ft) 

Long. 12.0 m (39.4 ft) 

Lat. 4.6 m (15.1 ft) 

Long. 17.1 m (56.1 ft) 

L

Lo

Lat. 5.0 m (16.4 ft) 

Long. 10 m (32.8 ft) 

Lat. 0.0 m (0.0 ft) 

Long. 15.2 m (49.9 ft) Tangent SKT 

Energy Absorbing Lat. 5.7 m (18.7 ft) Long. 8.5 m (27.9 ft) Lat. 0.0 m (0.0 ft) Long. 17.5 m (57.4 ft) 

Lat. 2.0 m (6.6 ft) 

Long. 37.0 m (121 ft) 

L

Lat. 1.7 m (5.6 ft) 

**Long. 32.0 m (105 ft) 

Flared 

FLEAT 

Energy Absorbing 

Lat. 0.0 m (0.0 ft) 

Long. 5.5 m (18.0 ft) Lat. 1.6 m (5.3 ft) 

Long. 9.7 m (31.8 ft) 

Did Not Conduct 

Lat. 3.0 m (9.8 ft) 

Long. 19.0 m (62.3 ft) 

Lat. 1.0 m (3.3 ft) 

Long. 44.0 m (144 ft) 

Flared 

REGENT 

Non-Energy Absorbing Lat. 1.5 m (4.9 ft) Long. 29.5 m (96.8 ft) Lat. 4.6 m (15.1 ft) Long. 77.2 m (253 ft) 

Did Not Conduct 

Lat. 5.2 m (17.1 ft) 

Long. 41.8 m (137 ft) 

Flared 

SRT 

Non-Energy Absorbing 

Numbers Were 

Not Reported Lat. Not Reported 

Long. Past the 53.3 m 

(175 ft) test installation 

Did Not Conduct 

** The FLEAT 3-31 Long. 32.0 m (105 ft) value is from a test involving the impact head deforming sufficiently to block the ra

stopped after only about 1.5 m (5 ft). When the impact head was further reinforced to prevent this behavior the vehicle stopp
Post Impact Vehicle Trajectories 

(Shown are Final Resting Positions for Various NCHRP 350 Roadside T

 H L 

 D 

C 

A 

P 

Q Q G 

P 

K + 

O O J 

 350’ 300’ 250’ 200’ 150’ 100’ 50

A – BEST Terminal Test 3-30 

B – BEST Terminal Test 3-31 

C – BEST Terminal Test 3-32 + N (early 

D – BEST Terminal Test 3-33

E – ET Terminal Test 3-30

F – ET Terminal Test 3-31

G – ET Terminal Test 3-32

H – ET Terminal Test 3-33

I – SKT Terminal Test 3-30

J – SKT Terminal Test 3-31

K – SKT Terminal Test 3-32

L – SKT Terminal Test 3-33

M – FLEAT Terminal Test 3-30

N – FLEAT Terminal Test 3-31

O – REGENT Terminal Test 3-30

P – REGENT Terminal Test 3-31

Q – SRT Terminal Test 3-31 

23 m (75 ft) x 6 m Area as Described AASHTO RDG Sec

Non-Energy Absorbing Terminals: Recommended Minimum 175 ft. Clear Area Vehicle Can Travel. Refer to FHWA Accept

• CC-56A – MNDOT – Eccentric Loader • CC-72 – Trinity Industries – Slotted R• CC-80 – Energy Absorption Systems • CC-84 – CTDOT – TL-2 MELT Termina

Vehicles May Travel Over 75 m (250 ft) With Non-Energy Absorbing Terminals