Highway Design Implications
Reducing Bottlenecks: Physical Design
Clearly one wants to design freeways to high
standards, i.e., design for highest nominal
capacity possible.
Roadways need to be carefully designed to
reduce/mitigate bottlenecks:
Lane dr

Volume-Delay Functions
We have also seen that cumulative count curves can be used to
compute delay for very simplified deterministic queuing processes.
Can we construct simple but robust models of road segment travel
times of the form:
t = t(q,Z) where

1
All figures and tables in these notes are from TRB Special Report 209.
1. Definitions
2. Basic freeway sections
3. Weaving sections
4. Ramps
Highway
1
Capacity
Number & width of lanes
Right-shoulder lateral clearance
Interchange spacing
Vertical alignme

Shock Waves & Kinematics
1. Shock waves
2. Kinematic theory of traffic flow
Shock-waves occur whenever
there is a sudden/discontinuous
change from one stable (k,v)
domain to another.
Shock-Waves
T
Shock-waves at beginning
and end of zero-flow region
cause

(1) Speed Flow Density
(2) Level of Service
Traffic Stream Relationships
If we assume that v is a linear function
of density (upper left diagram) then we
get a simple model that allows us to
solve for any relationship between
flow, speed & density.
Fundam

A Few Fundamentals
Performance measures
Roads as queuing systems
Stochastic queues
Deterministic queues
Sequences of queues
Time-space diagrams
Fundamental flow equation
Shock-waves
Cumulative count curves
Fluid-flow approximation
Delay
Oversatura

1. Introduction to gap acceptance
models
2. Lane-Changing
Gap Acceptance & Lane
Changing
Any time a vehicle has to cross or merge into a vehicle
stream, the driver faces a gap acceptance problem; i.e.,
s/he must decide whether s/he can safely move
throug

Traffic Signal Systems
1. Signal Actuation
2. Signal Progression
Signal Actuation
Fixed/pre-timed signals obviously cannot respond to traffic dynamics; while
possibly optimized for average conditions, they may well be sub-optimal for actual
traffic flows.

Performance of Streets:
Introduction
Types of Intersections
Intersection Conflict Points
The primary concern in
intersection design is to control
movements through the
intersection so as to permit
conflicting movements to safely
share the intersection spa