materials developed by k. watkins, j. lamondia and c. brakewood frequency determination unit 5:...

Materials developed by K. Watkins, J. LaMondia and C. Brakewood

Frequency Determination

Unit 5: Staff & Fleet Scheduling


Service Planning Steps

Crew scheduling

Vehicle scheduling

Timetabling

Frequency determination

Route design and stop layout

Network design


Agenda

• Understand the importance of varying route frequencies

• Discuss different approaches for determining frequencies

• Calculate demand-based frequencies

• Displaying variable frequencies in maps and signage


Frequency Determination

… is how often a vehicle will come by any given transit stop on a route

… also known as “headways”

… is critical to ensuringcost-effective, efficient service


Frequencies are Variable

• Vary by route, time of day, day of week, day type


Many Types of Service

• Express Bus• Priority Service• Local• Feeder• Circular


Varying Frequencies is Useful

It allows us to…• Identify important routes• Create system hierarchy• Improve flow between areas• Facilitate rider understanding• Support different trip purposes• Maintain a cost-effective system


Why can’t we make every route very frequent?


Balancing Cost and Frequency

• It would be great to have fast/ frequent service on every route, but it would result in:– Many buses and drivers– Empty vehicles– High operating costs– Roadway congestion

• So how do we figure out the best frequency to use?


Three Main Approaches

• Policy-based Frequencies– Service meeting fed/state mandates

• Performance-based frequencies– Service meeting fed/state objectives

• Demand-based Frequencies– Service meeting ridership needs


Policy-based Frequencies

• Often decided by – Experience– Judgment– Simple passenger counts

• General standards (minutes)– 15 to 20 – peak, high frequency– 20 to 60 – off peak, low frequency


Policy-based Frequencies

• Consistent and fixed intervals between vehicles on the route – all day, every day

• Best in areas with low passenger demand

• Most likely clock intervals– Repeating at set 10, 15, 20 minutes


Performance-based Frequencies

• Fixed to be goal oriented

• Based on targeted performance standards over a given service day

• Typically measure non-transit characteristics OR are determined by optimization


MAP-21 Transit Performance

• All about optimization!!


Demand-based Frequencies

• Most commonly used approach

• Service provided is directly related to – the number of passengers riding at a given time – the vehicle capacity required to carry them


Demand-based Frequencies

• Best in areas where the demand varies throughout the day

• Meet demand subject to constraints including peak loading, policy headways and productivity


Demand-based Techniques

• Three main calculations used to determine this frequency

• Practitioners do all 3, pick the best

• Based on – Point Check Counts– Ride Check Counts


Collecting Point Check Data

• Team of trained engineers & planners – One at each stop location on the route• Usually known busiest route

– Decide on set time periods– Record number of riders seen at each stop

location– Usually completed several times a year


Example

Stop Number

Distance to Next Stop

Average Observed Load by HourTotal

Passengers6-7am 7-8am 8-9am 9-10am 10-11am

1 2 mi 50 136 245 250 95 776

2 1 mi 100 510 310 208 122 1250

3 1.5 mi 400 420 400 320 200 1740

4 3 mi 135 335 350 166 220 1206

5 2.5 mi 32 210 300 78 105 725


Method 1 (Point Check)

Frequency =

Volume at the Daily Max Load PointDesired Occupancy

Identifies headways that provide the best service to the one stop that is busiest over

the entire day


Method 1 Data

Stop Number




1 2 mi 50 136 245 250 95 776

2 1 mi 100 510 310 208 122 1250

3 1.5 mi 400 420 400 320 200 1740

4 3 mi 135 335 350 166 220 1206

5 2.5 mi 32 210 300 78 105 725


Method 1 Frequencies

Period Calculation Frequency (veh/hr)

Headway (minutes)

6-7am 400 observed passengers / 50 person capacity 8.0 7.5

7-8am 420 observed passengers / 50 person capacity 8.4 7





Method 2 (Point Check)

Frequency =

Volume at the Hourly Max Load PointDesired Vehicle Occupancy

Identifies headways that provide the best service to

specific stops that arebusiest during each time period


Method 2 Data

Stop Number




1 2 mi 50 136 245 250 95 776

2 1 mi 100 510 310 208 122 1250

3 1.5 mi 400 420 400 320 200 1740

4 3 mi 135 335 350 166 220 1206

5 2.5 mi 32 210 300 78 105 725



Period CalculationFrequency

(veh/hr)Headway (minutes)







Collecting Ride Check Data

• Automatic Passenger Counters (APCs) – Onboard every route– Decide on set time periods– Record number of riders boarding and alighting at

each stop location– Tells us load variability across a route– Usually completed several times a year


Example


Method 3 (Ride Check)

Frequency =

MAX of… Passenger Load Space (Passenger-km)___ Desired Vehicle Occupancy x Route Length (km)

ORVolume at Hourly Max Load Point

Vehicle Capacity


Method 3 (Ride Check)

Identifies headways that minimize the load variability across an entire

routeduring the busiest time period


Method 3 Data



For 6-7am:Area in passenger-km: (50*2+100*1+400*1.5+135*3+32*2.5)=1285Desired vehicle occupancy: 50 passengersRoute Length: 10km

Volume at Hourly Max Load Point: 400 passengers (from table before)Vehicle Capacity: 90 passengers (given)

Option 1: 1285 / (50*10) = 2.57

Option 2: 400 / 90 = 4.44

Pick the larger: 4.44 vehicles/hour


Method 3 Data


Class Exercise

For 8-9am: refer to diagramArea in passenger-km: Desired vehicle occupancy:Route Length:

Volume at Hourly Max Load Point:Vehicle Capacity:

Option 1:

Option 2:

Pick the larger: vehicles/hour



Period Frequency (veh/hr)

Headway (minutes)

6-7am 4.44 14

7-8am 5.88 10

8-9am 6.40 9

9-10am 3.72 16

10-11am 3.07 20


So Which Method is Better?

• Which is more important?

• Peak day… Method 1• Peak hours… Method 2• Route variability… Method 3


A Note on Finishing Calculations

• Headways should always be rounded down to the next minute

• If clock headways, round to appropriate minute on schedule


Displaying Frequencies

• Most transit maps highlight routes

• Do not designate differences between them

• Is this a concern?


Display Concerns

• Yes! Not all routes are equal

• It shows us anticipated speeds, wait times, service times

• Emphasizes network aspect of the transit system


Displaying routes


Frequency Map


Conclusion

• Routes must vary in frequency.

• There are 3 main approaches for coming up with these frequencies.

• Demand-based frequencies rely on capacity and ridership data.

• Frequencies need to be displayed.


Reference

Materials in this lecture were taken from:• Mark Hickman, Fundamentals of Transportation

wikibook, “Network Design & Frequency”, http://en.wikibooks.org/wiki/Fundamentals_of_Transportation/Network_Design_and_Frequency

• Chapter 8 of the TCRP “Transit Capacity and Quality of Service Manual, 3rd edition”, 2013.

http://en.wikibooks.org/wiki/Fundamentals_of_Transportation/Network_Design_and_Frequency



materials developed by k. watkins, j. lamondia and c. brakewood frequency determination unit 5:...

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