Delay and Offset

1

• Topic 6
• Delay and Offset

2
Delay

• Delay the most commonly used performance measure
  
• Types of Intersection Delays
• Stopped delay
• Total delay (control delay)
• Time in queue delay

3
Delay Studies
Distance
Total Delay (Control Delay)
Stopped Delay
Stop Line
Deceleration
Acceleration
Time
4
Time in Queue Delay
Distance
Stopped Delay
Stop Line
Time in Queue Delay
Time
5
The HCM Delay Equation
Uniform Delay
6
Uniform Delay
Cumulative Arrival
V
S
r
g0
Cumulative Departure
g
C
7
Uniform Delay
V
Cumulative Arrival
S
S
Cumulative Departure
C
C
8
Random and Over-saturation Delay
V
S
Cumulative Arrival
S
Cumulative Departure
C
C
9
Delay with Initial Queue
V
S
Cumulative Arrival
S
Cumulative Departure
C
C
10
Uniform Delay with Platoon Arrival(Platoon on
Red)
N
Cumulative Arrival
Vnp
Vp
S
r
g
Cumulative Departure
C
11
Uniform Delay with Platoon Arrival(Platoon on
Green)
N
Vp
Cumulative Arrival
Vnp
S
r
g
Cumulative Departure
C
12
Example
Assume a two-lane one-way street links two
intersections i and j, which is 800 feet apart.
The one-way link flow is all through traffic and
has a volume of 1000 vph. Saturation flow rate is
all 1800 vphpl. Assume vehicle travel speed is 25
mph. The system cycle is 70 sec, and the
effective arterial through greens for the
upstream (i) and downstream (j) intersections are
35 sec and 30 sec, respectively. The offsets are
0 and 20 sec for the two intersections,
referencing to the start of green of the arterial
phases (i.e., arterial phase green at j starts 20
sec later after i). Calculate the uniform
delay at intersection j considering (1) no
platoon dispersion (2) with platoon dispersion
(a0.35, ß0.80) (3) What if the offset is 40
sec?
13
No Platoon Dispersion
s
Flow Rate
v
t0
Time
ru
gu
C
s
T.T
v
?
Time
rd
gd
C
14
Offset - 20
Delay 3.7 sec/veh
15
Offset - 40
Delay 13.6 sec/veh