Jeffrey M. Sims ● President 

 7001 Heritage Village Plaza ● Suite 220 ● Gainesville, VA 20155 ● 703-549-3010 

Attn: Tad Wysor December 15, 2014 

The following trailer types should be excluded from all aerodynamic type devices in the GHG2 

rulemaking, as defined in the TTMA Publications RP No. 36 Tank Trailer Nomenclature and RP No. 66 

Trailer Nomenclature. (see definitions below) 

For bulk tank trailers, a very few of these designs have had aero devices fitted or proven out: most 

efforts focus on non-spec, food grade, and certain DOT-407 tanks. DOT-406 tanks (commonly gasoline 

tankers) are most often fitted with extensive piping (qualifying as work performing equipment) that would 

preclude most aerodynamic devices. DOT-412 should not be fitted with aerodynamic devices as they 

might interfere with the safe operation of these corrosive carrying tankers which need routine external 

examination of the shell. Until the possibilities of aerodynamic devices on cargo tanks are better 

understood, these categories of trailers should have goals set consistent with no aerodynamic devices 

fitted. 

Similarly, Aero devices fitted to Platform (Flatbed) trailers [A trailer chassis consisting of load 

carrying main frames and a flat loading deck without permanent sides or roof.] have had little to no track 

record, as the load carried predominates any Cd issues. These trailers should be grouped with bulk tank 

trailers and have goals consistent with no aerodynamic devices fitted. 

For a discussion of Van-type trailers, please examine the spreadsheet that follows the definitions 

below. 

TRAILER, AGRICULTURAL COMMODITY: 

Agricultural commodity trailer means a trailer that is designed to transport bulk agricultural commodities in 

off-road harvesting sites and to a processing plant or storage location, as evidenced by skeletal construction 

that accommodates harvest containers, a maximum length of 28 feet, and an arrangement of air control lines 

and reservoirs that minimizes damage in field operations.571.121 

TRAILER, AUTO TRANSPORTER: 

The semi trailer portion of an auto transporter truck and trailer combination designed and manufactured 

expressly for the loading, transportation and unloading of automobiles. 

TRAILER, CONTAINER CHASSIS: 

A semi trailer chassis designed especially to transport one or two containers over the highway. 
TRAILER, DROP CENTER (DOUBLE DROP): 

A trailer design employing an offset or drop in the cargo deck immediately behind the supports and another 

immediately in front of the suspension, the purpose of which is to lower the cargo deck and/or to provide the 

greatest height possible for cargo in the dropped area. 

TRAILER, DROP FRAME: 

Trailer designs employing one offset or drop in the cargo deck immediately behind the supports. 

TRAILER, DUMP: 

Trailer designed to haul bulk cargo and unload through gravity discharge, either though end door(s) and 

tilting or bottom doors. 

TRAILER, HEAVY HAULER: 

Heavy hauler trailer means a trailer which has one or more of the following characteristics, but which is 

not a container chassis trailer: 

 (1) Its brake lines are designed to adapt to separation or extension of the vehicle frame; or 

 (2) Its body consists only of a platform whose primary cargo-carrying surface is not more than 40 

inches above the ground in an unloaded condition, except that it may include sides that are designed to be 

easily removable and a permanent ``front end structure'' as that term is used in Sec. 393.106 of this title. 

571.121 

TRAILER, HORIZONTAL DISCHARGE: 

Trailers that are used in the road construction industry to deliver asphalt and other road building materials to 

construction sites (``the trailers''). The trailers are designed to connect with and latch onto various paving 

machines (``pavers''). With their hydraulically controlled horizontal discharge systems, the trailers discharge 

hot mix asphalt at a controlled rate into pavers which overlay the road surface with asphalt material. 

TRAILER, LOWBED: 

A platform trailer constructed to provide minimal ground clearance beneath the loading deck and designed to 

transport heavy, often times concentrated loads with high centers of gravity. 

TRAILER, LOWBED, LEVEL DECK: 

A lowbed trailer with the deck level from the back of the gooseneck to the rear of the trailer. 

TRAILER, OILFIELD FLOAT (OILFIELD FLATBED): 

A flatbed equipped with a pick-up loop at the front for a winch line and with provision in the area of the 

supports to allow the nose of the trailer to be lowered to the ground for loading or unloading. Oilfield floats 

are normally equipped with a rolling tailpipe across the rear. 

TRAILER, POLE: 

Pole trailer means a motor vehicle without motive power designed to be drawn by another motor vehicle and 

attached to the towing vehicle by means of a reach or pole, or by being boomed or otherwise secured to the 

towing vehicle, for transporting long or irregularly shaped loads such as poles, pipes, or structural members 

capable generally of sustaining themselves as beams between the supporting connections. 571.3 
TRAILER, STRADDLE: 

Straddle trailer means a trailer that is designed to transport bulk agricultural commodities from the 

harvesting location as evidenced by a framework that is driven over the cargo and lifting arms that suspend 

the cargo for transit. 571.121 

TANK, DOT 406: 

Tank built after August 31, 1995 must comply with U.S. DOT specification DOT 406 as defined in 49 

Code of Federal Regulations 178.346. This tank is typically used to carry gasoline, fuel oil, alcohol, or 

other liquid flammables. This tank is typically constructed of aluminum and designed with an elliptical 

straight or double cross section. 

TANK, DOT 407: 

Tank built after August 31, 1995 must comply with U.S. DOT specification DOT 407 as defined in 49 

Code of Federal Regulations 178.347. This tank is typically used to carry solvents, plasticizers, casing 

head, gas, etc. This tank is typically constructed of stainless steel or aluminum and designed for pressure of 

at least 25 psig. 

TANK, DOT 412: 

Tank built after August 31, 1995 must comply with U.S. DOT specifications DOT 412 as defined in 49 

Code of Federal Regulations 178.348. This tank is typically used to carry corrosives. This tank is typically 

constructed of stainless steel or carbon steel and designed for a pressure of 35 psig. 

TANK, DRY BULK: 

A tank typically constructed of aluminum or carbon steel to carry dry bulk commodities such as cement, 

fertilizer, sand, plastics, grain, etc. with typical densities ranging from 18 to 125 pounds per cubic foot. 

This tank is typically designed for an unloading pressure of 15 psig. 

TANK, FRAC: 

A portable storage tank used to hold flushing or fracing fluid at an oil well site. Characterized by a large 

rectangular cross section, a single axle suspension, no landing gear, and a front winching bar. 

TANK, HOT PRODUCTS: 

A tank typically insulated to handle asphalt and other products at a temperature over 300°F. This tank is 

typically constructed of aluminum, steel, or stainless steel and designed for atmospheric pressure. 

TANK, MC 331: 

Tank meeting U.S. DOT Specification MC 331 as defined in 49 Code of Federal Regulations 178.337. This 

tank is typically used to carry anhydrous ammonia, propane, or other liquefied or pressurized gases. This 

tank is typically constructed of quenched and tempered or carbon steel and designed for a pressure of 265 

psig. 

TANK, MC 338: 

Tank built after October 1, 1984, meeting U.S. DOT Specification MC 338 as defined in 49 Code of 

Federal Regulations 178.338. This tank is insulated and designed to carry cryogenic liquids. 
TANK, NON-SPEC: 

A tank not meeting one of the U.S. DOT Specifications. 

TANK, SANITARY: 

A tank typically insulated to carry milk, vinegar, vegetable oils, syrups, and other food products. This tank 

is typically constructed of stainless steel and designed for atmospheric pressure. 

TANK, SELF SUPPORTING: 

A tank trailer whose shell is the structural support member for the vehicle. 

TANK, TOFC: 

A tank meeting Association of American Railroads Specification M-931, Appendix F. This tank is a MC 

307, MC 312, DOT 407, DOT 412 or IMCO Type 4 tank constructed of steel with a minimum design 

pressure of 35 psig. This tank trailer is for trailers on railroad flat car service. 

TANK, VACUUM: 

Tank equipped with a pump to reduce the pressure in the tank to much less than atmospheric pressure. This 

reduced pressure or "vacuum" is used for loading the tank. (See Tank, Waste). Also See 49 CFR 178.345-

1(c). 

TANK, VARIABLE SPECIFICATION: 

A cargo tank that may be physically altered to conform to another cargo tank specification must have the 

required physical alterations to convert from one specification to another clearly indicated on the variable 

specification plate. (49 CFR 178.345-1(c)) 

TANK, WASTE: 

Tank designed to transport waste consisting of liquid and/or solids. Tank may have a full opening rear 

head. Tank may be equipped for vacuum loading.
Vans

Aero Reqd? Enhanced Aero Reqd? LRR Tires Required? ATIS Reqd? Style Length Yes Maybe Eventually Yes Yes Straight Floored 53' lengtMaybe Eventually Maybe Eventually Maybe Eventually Yes No No No No No No Yes Yes Other leNo No Maybe Eventually Yes No No No No No No Yes Yes Drop Deck 53' lengtNo No Maybe Eventually Yes No No No No No No ? ? No No Yes Yes Other leNo No Maybe Eventually Yes No No No No No No ? ? Yes No Yes Yes Long 

Combination 

Vehicle (w/ 

Pintle Hook) 

53' lengt

Maybe Eventually No Maybe Eventually Yes Yes No Yes Yes 48' lengtMaybe Eventually No Maybe Eventually Yes Yes unless other exclusions apply No Maybe Eventually Yes 33' lengtYes unless other exclusions apply No Maybe Eventually Yes 28' lengtYes unless other exclusions apply No Maybe Eventually Yes Other leYes unless other exclusions apply No Maybe Eventually ? (less tha

Exclusions 

Vans or reefers with work performing devices under the belly (aero exclusions) (e.g. Side doors under belly mounted steps) 

Rear lift gates or rail lifts excluded as short distance haulers Pintle hooks excluded from enhanced aero Exterior post/roof bow trailers by necessity (refuse, chip hauler etc.) excluded for off road/aero/tires TOFC trailers Livestock Trailers with perforated sides Trailers intended for storage/office use Rollup rear doors excluded for enhanced aero Reefer units/nose & rear vents may preclude enhanced aero. Off road or vocational