Vehicle Weight Definitions

The operator is responsible for knowing how much weight is loaded on the tractor-trailer and knowing the total weight of both the unit and cargo. The terms used for vehicle weight is as follows:

Payload allowance or payload is the maximum weight of material that can be transported.

Gross vehicle weight (GVW) is the total weight of a single vehicle plus its load.

Gross combination weight (GCW) is the total weight of a powered unit including the trailer(s) and cargo.

Gross vehicle weight rating (GVWR) is the maximum GVW specified by the manufacturer for a single vehicle, including the load.

Gross combination weight rating (GCWR)is the maximum GCW specified by the manufacturer for a specific combination of vehicles, including the load.

Curb weight is the total weight of the empty truck with the fuel tank, cooling system, and crankcase filled. Additionally, it also includes the weight of tools, spare tire, and all other equipment specified as standard. However, this weight does not include the weight of the payload and operator.

Axle weight is the weight transmitted to the ground by one axle or one set of axles.

Tire load is the maximum safe weight a tire can carry at a specified pressure. This rating is stated on the side of each tire.

Suspension systems have a manufacturer's weight capacity rating.

Coupling device capacity are rated for the maximum weight they can pull and/or carry.

Operating Conditions

The maximum payload of a truck is determined by subtracting the curb weight and weight of the driver (175 pounds) from the manufacturer's gross vehicle weight rating. The maximum gross vehicle weight rating for a specified operating condition applies only when the tires and equipment on the truck are according

Figure 7-27.-Reflective triangle placement: one way or divided highway.

rule of thumb used for measuring how much distance you should maintain from the vehicle in front of you is at least 1 second for each 10 feet of vehicle length at speeds below 40 mph. At greater speeds, you must add 1 second for safety; for example, if you are operating a 40-foot vehicle, you should allow at least 4 seconds between you and the vehicle ahead. In a 60-foot tractortrailer, you need 6 seconds. For over 40 mph, you need 5 seconds for a 40-foot vehicle and 7 seconds for a 60-foot tractor and trailer.

To measure distances, wait until the vehicle ahead passes a shadow on the road, a pavement marking, or some clear landmark. Then count off the seconds as "one thousand-and-one, one thousand-and-two" and so forth, until your vehicle reaches the same spot. Compare your count with the rule of 1 second for every 10 feet of length. If you are operating a 40-foot truck and only counted up to 2 seconds, you are too close.

LOADING AND SECURING CARGO

As a tractor-trailer operator, you must have an understanding of the basic procedures and safety rules used when transporting construction supplies and equipment. Improper loading of any load can be a danger to yourself and others around you, cause damage to the tractor-trailer, affect the steering of the tractor, and so forth. The operator, whether or not you loaded and secured the load yourself, is responsible to inspect the load, to recognize overloads and poorly balanced

Figure 7-28.-Correct placement of payload.

to the manufacturer's recommendations for the specified operating condition; that is, ideal, moderate, or severe.

IDEAL CONDITION.- An ideal condition is when a truck is operated over improved, level roads, such as asphalt or concrete, at constant, relatively moderate speeds with no adverse weather or road conditions. Under these conditions, recommended payload equals 100 percent of maximum permissible payload.

MODERATE CONDITION.- A moderate condition is when a truck is operated at high speeds over improved highways, such as asphalt or concrete, with or without long or steep grades. Moderate conditions also include operating at moderate speeds over semiimproved roads with gravel or equivalent surfacing, in gently rolling country with few steep grades and no adverse weather or road conditions. Under these conditions, recommended payload equals 80 percent of maximum permissible payload.

SEVERE CONDITION.- A severe condition is when the vehicle is operated off the highway on rough or hilly terrain or over unimproved or pioneer access roads with deep ruts, holes, or steep grades. These conditions also include operating where traffic has created deep holes or ruts in heavy snow, covering normally good city streets or highways. Under these conditions, the recommended payload equals 64 percent of the maximum permissible payload.