Describe the possible situations that would require adjustments from the base conditions for freeway capacity analysis.

Question

What will be an ideal response?

Answer 1

Base conditions are the criteria that must be satisfied if a basic freeway
segment is to operate at the maximum capacities. If one or more of the following
conditions is not met, the capacity of the segment will be reduced.
(1) Weather and driver visibility are good and do not affect traffic flow.
There are no obstructions that could impede traffic flow such as incidents,
accidents or roadwork. The HCM 2010 capacity procedure does not offer a
computational compensation factor for these conditions. Accordingly, the
procedure is based on the assumption that each condition is met.
(2) The traffic stream is composed solely of passenger cars and there are
no heavy vehicles such as trucks, buses and recreational vehicles (RVs).
(3) Traffic lanes are at least 12-ft wide and a right-side clearance exists
that is at least 6-ft wide.
(4) All drivers in the traffic stream are regular users and are familiar with
the freeway segment.
(5) The total ramp density is zero. Ramp density is the total number of on
and off ramps per mile in one direction within the freeway segment under study.
For the ramp density to be zero, there are no ramps within the segment. The HCM
2010 capacity procedure for Basic Freeway Segments applies to segments no
greater than 6 miles long.
(6) A state of unsaturated flow must exist for the HCM 2010 procedures to
apply. This state occurs when the traffic stream is unaffected by upstream or
downstream bottlenecks.