Adequacy Analysis
The adequacy of a parking facility can be measured by calculating the probability that
an entering vehicle will not be able to find a parking space. A high probability of
rejection (not finding a space) may indicate that expansion of the parking facility is
warranted.
The probability of rejection can be calculated by comparing the traffic load to the
number of parking stalls as shown below.
First, the traffic load is estimated using:
A = Q*T
Where:
A = traffic load,
Q = incoming vehicle flow rate, and
T = the average parking duration.
Make sure that your units of time cancel each other. If you give Q in vehicles per
hour, then use T in units of hours.
Next, calculate the probability of rejection using the following formula:
P = (AM/M!)/(1 + A + A2/2 + . . . + AM/M!)
Where:
P = the probability of rejection,
A = the traffic load, and
M = the number of parking stalls.
If the probability of rejection is high, you may want to consider adding more parking
stalls to the parking facility.
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