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Getting Started - Page 7 of 8

ID# C3GS007

Getting Started

We must refer to HCM Chapters 12 and 20 to determine the information required for LOS estimation on two-lane highways. Referring to Chapter 12 (Highway Concepts), we are able to learn that the determination of the highway Class is related more to the general nature of the highway and to motorist expectations than to quantitative field data. Unlike signalized arterials, there is no segmentation involved in a two-lane highway analysis. The facility is assumed to be homogeneous, and heterogeneous segments should be analyzed as separate facilities.

The following information is needed to produce an estimate of the LOS for a two-lane highway:

Exhibit 3-6. Information Required to Determine Two-lane Highway Level of Service
Data Item Source or Assumptions
Highway Class (I or II) To be determined in Problem 1
Facility length Scaled from map
Lane width Measured at 12 ft for the whole facility
Shoulder width Measured at 3-5 ft.
Terrain Always flat, consistent with its coastal Florida location
Traffic volume Based on traffic counts
PHF Based on field measurements
Directional split Based on field measurements
Trucks and buses (%) Based on field measurements
Recreational vehicles (%) Will be aggregated with trucks and buses
No passing zones (%) Based on field measurements
Access points per mile Based on field measurements
Free flow speed Base free flow speed will be assumed to be the posted speed + 5 mph.  The actual free flow speed will be calculated from other data items indicated above, using the HCM Chapter 20 procedure.

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