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Pages 46-58

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From page 46...
... 46 This section reviews the current national and statewide truck classification schemes and recommends an appropriate classification scheme for use in the analysis of the effects of trucks on other modes and the effects of other modes on the quality of service experienced by trucks on the highways. Two characteristics of trucks are of primary importance when predicting the effect of trucks on facility performance and vice versa: truck length and the ratio of weight to power.4 There are numerous truck classification schemes currently in use in the United States, and each was developed for a different purpose.
From page 47...
... Recommended HcM truck classification Scheme 47 5.1 Existing National Truck Classification Schemes There are four basic national truck classification schemes and several variations on these schemes (see Exhibit 18)
From page 48...
... 48 Incorporating Truck Analysis into the Highway Capacity Manual 5.1.1 NHTSA Classification Scheme Vehicle manufacturers are required by federal regulations (Title 49 Code of Federal Regulations, Chapter V, Section 565.6) to submit information on the gross vehicle weight rating (GVWR)
From page 49...
... Recommended HCM Truck Classification Scheme 49 Class Illustration Description 1 Motorcycles: All two or three-wheeled motorized vehicles. 2 Passenger Cars: All sedans, coupes, and station wagons manufactured primarily for the purpose of carrying passengers and including those passenger cars pulling recreational or other light trailers.
From page 50...
... 50 Incorporating Truck Analysis into the Highway Capacity Manual Class Weight (pounds) Power (hp)
From page 51...
... Recommended HcM truck classification Scheme 51 Truck Tractor-Semitrailer (Single-Trailer) Combinations The minimum length set for the semitrailer in a single-trailer combination is 48 ft., which can be higher depending on the grandfathered limit for a particular state.
From page 52...
... 52 incorporating truck Analysis into the Highway capacity Manual the AASHTO design vehicles is to ensure adequate lane widths, turning radii, and other geometric features for trucks in the design of streets and highways. 5.2 Other Classification Schemes Besides axles, the number of trailers, weight, and trailer length, there are other classification schemes based on overall length (facilitates automated counts)
From page 53...
... Recommended HcM truck classification Scheme 53 5.3 HCM Vehicle Classification HCM classifications were developed to assess the effects of trucks on highway capacity. The HCM defines three non-automobile vehicle types: transit buses, RVs, and trucks.
From page 54...
... 54 incorporating truck Analysis into the Highway capacity Manual simplistic approach was taken by the HCM to reduce data collection requirements for capacity analysis. However, with the new automated data collection sources available (specifically Weighin-Motion)
From page 55...
... Recommended HcM truck classification Scheme 55 Weight-to-horsepower also determines how quickly a vehicle can accelerate from a standing start. This is an important factor when trucks operate on signalized roadways (arterials)
From page 56...
... 56 incorporating truck Analysis into the Highway capacity Manual time intervals. A digitizer converts the frames into digital signals that are sent to a computer for extraction of vehicle features.
From page 57...
... Recommended HcM truck classification Scheme 57 The ideal truck classification scheme would take into account • Truck length and weight-to-horsepower ratio (so as to estimate the capacity and speed effects of trucks on automobile traffic) and • Whether the truck is loaded or unloaded and the value of the goods carried (so as to estimate the importance of reliability and average travel time to trucks)
From page 58...
... 58 incorporating truck Analysis into the Highway capacity Manual Future research may be able to develop data collection methods so that analysts conducting capacity analyses can segregate the single unit trucks and the semitrailer trucks observed on a given facility by their weight-to-horsepower ratio, thereby further refining their ability to estimate the capacity and speed effects of trucks. Note that motorcycles, passenger vehicles, and buses are not the subject of the current research project.

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