Roadway Functional Classification

NDOT roadway classifications are presented in Figure IV-h (Jan. 15, 2003). These roadway classifications help the State group similar roadway data to estimate truck traffic, accidents and daily traffic.

  • I-80 is classified as an "Interstate Highway
  • US 50 is classified as an "Other Principal Arteria
  • SR 278 is classified as a "Rural Major Collector

Truck Percentages
NDOT has provided truck percentages based on functional classification as follows:

I-80 - Interstate Highway

32.3% Trucks

US 50 - Other Principal Arterial

19.6% Trucks

SR 278 - Rural Major Collector

12.9% Trucks

Trucks create potentially hazardous conditions in roadways including faster road surface wear and potentially slower moving vehicles in hilly areas. In addition, trucks often are less stable than smaller vehicles on steep downgrades, leading to the potential for crashes.

Figure IV-h  NDOT Functional Classification

Annual Average Daily Traffic

NDOT publishes traffic count data in an Annual Traffic Report. The most current traffic report at the start of this project used to establish daily traffic counts was the 2003 report. Exhibits 3 through 7 display NDOT count locations and traffic volumes.

Traffic counts are usually performed for a five to seven-day period and divided by the number of hours sampled, then multiplied by 24 (24 hours in a day). The count is factored (seasonal, etc.) and annualized over the entire year. This method includes weekend traffic. AADT is not the same as Average Daily Traffic (ADT) which estimates traffic on a typical weekday (Tuesday through Thursday). AADT is used for maintaining large road networks (statewide) while ADT is typically used for localized traffic impacts from development.

Figure IV-i below displays traffic count station locations and volumes on I-80 and the on/off ramps within Eureka County. Each of these numbers represents a traffic monitoring station number that is used on look-up tables to obtain historical and recent traffic volumes (see Appendix J).

Figure IV - i
NDOT Traffic Count Stations on I-80 (Eureka County)

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