Parking Maneuvers

1
Parking Maneuvers
2
Overview of Presentation

• Project Objective
• Saturation flow rate-Definition
• Adjustment factors to determine saturation
  flow-rate
• Data analysis in areas of interest
• Downtown
• Northwest-Pearl District
• Streets of Tanasbourne

3
Project Objective

• Examine urban areas with high on-street parking
  turnover.
• Determine average times for parking maneuvers.
• Entrance times
• Exit times
• Determine number of parking maneuvers per hour.
• Can be obtained through field study
• Smart park meters give data obtaining to
  maneuvers per hour
• Calculate parking adjustment factor fp based on
  the HCM average parking maneuver time versus
  measured field times.

4
Saturation Flow-Rate

• The saturation flow rate is the maximum hourly
  volume that can pass through an intersection,
  from a given lane group or group of lanes
  (Mannering et. Al pg. 226.)
• The HCM states a typical base saturation flow
  rate of 1900 (pc/h/ln) is possible at
  intersections.
• When calculating base saturation flow there are a
  number of adjustment factors which reduce flow.
• These factors include lane widths, grades,
  parking maneuvers, bus blockage, pedestrian and
  bicycle activity, etc.

5
Saturation Flow Rate Adjustment Factors

• Base saturation flow rate is 1900 pc/h/ln.
• The variable fp is the parking adjustment factor
  in the saturation flow formula.
• The parking adjustment factor is a function of
  the number of lanes in a lane group and number of
  parking maneuvers per hour.
• The HCM states that each maneuver (either in or
  out) is assumed to block traffic in the lane next
  to the parking maneuver for an average of 18
  seconds.
• If more than a 180 parking maneuvers exist, a
  practical limit of 180 should be used (i.e.
  ).

6
Parking Maneuver Defaults

• The number of parking maneuvers is best measured
  in the field.
• In the absence of such data, it can be assumed
  from the number of parking spaces within 250 ft
  of the stop line and the average turnover rate
  for each space.
• The number of spaces within 250 ft of the stop is
  estimated assuming 25 ft per space.
• Therefore, each turnover (one car leaving and one
  car entering) generates two parking maneuvers.
• Exhibit 10-20 gives default values for maneuvers
  per hour, based on 80 percent occupancy of the
  spaces.

7
Downtown Portland
Measured average parking maneuver time was 4.73
seconds.
8
The Pearl District
Measured average parking maneuver time was 9
seconds.
9
Streets of Tanasbourne
Measured average parking maneuver time was 6.95
seconds.
10
Conclusions

• The assumed time of a parking maneuver as stated
  by the HCM is very conservative.
• The parking adjustment factor plays a significant
  role in calculating saturation flow rate.
• Analysis shows that parking maneuver times vary
  by location.
• More research necessary to finalize these values.