For two lane highway segments, can you calculate level of service on this section?
Description: Passing Constrained segment with horizontal curves
Type of Analysis: Operational analysis
This example problem illustrates the computation of LOS in a single direction of a curving, 0.75 mi-long Passing Constrained segment in level terrain.
The Facts
The segment to be evaluated has the same general demand and geometric characteristics as the segment evaluated in Example Problem 1.
The difference is that this segment has horizontal curvature instead of being straight; otherwise, the same inputs are used as for Example Problem 1.
The segment is split into 11 subsegments, with each subsegment being either straight (tangent) or curved. Horizontal curvature data for each subsegment is provided below.
Configuration from Exmaple Problem 1
- Segment length = 3,960 ft (0.75 mi);
- Segment type = Passing Constrained;
- No upstream passing lanes;
- Vehicle count in the analysis direction = 752 veh/h;
- PHF = 0.94;
- Posted speed limit: 50 mi/h;
- Percent heavy vehicles (%HV) = 5%;
- Percent grade = 0%;
- Horizontal curvature = none;
- Lane width = 12 ft;
- Shoulder width = 6 ft; and
- Access points = 0.
Subsegment Type, Length (ft), Superelevation (%), Radius (ft), Central Angle (deg), Horizontal Class
1 Tangent 280 -- -- -- --
2 Horizontal curve 432 3 450 55 3
3 Tangent 260 -- -- -- --
4 Horizontal curve 366.5 2 300 70 4
5 Tangent 250 -- -- -- --
6 Horizontal curve 216 5 275 45 5
7 Tangent 275.6 -- -- -- --
8 Horizontal curve 458 0 750 35 2
9 Tangent 285 -- -- -- --
10 Horizontal curve 767.9 4 1,100 40 1
11 Tangent 369 -- -- -- --
Total 3,960
Objective
Estimate the average speed in the subject direction on the two-lane highway segment, taking into account the effects of horizontal alignment on the average speed.
