§ 61.01 – What are the basic elements of collecting sample data?

(a)    Selecting a sample at random according to your sampling plan (Subsection 63).

(b)   Collecting data from the random sample (Subsection 65).

(c)    Identifying and correcting any errors in the sample data (Subsection 67).

§ 61.03 – What criteria does this section cover to ensure that estimates of annual service-consumed data meet FTA’s 95% confidence and 10% precision levels?

(a)    Your sampling process covers your entire service.

(b)   You select your sample at random according to your chosen ready-to-use sampling plan or your template sampling plan. 

(c)    Your data-collection process is designed to avoid errors from happening.

(d)   Your data-collection is designed to identify and correct errors when they occur. 

§ 63.01 – What are the basic elements of selecting a sample at random?

(a)    Choosing a method with which you select a sample at random.

(b)   Developing lists of service units that you expect to operate:

(1)   A single list of all services if your sampling plan is not based on service grouping.

(2)   One list for each service group if your sampling plan is based on service grouping.

(c)    Selecting a sample at random from each list with the chosen method.

§ 63.03 – What method may I use for random sampling?

(a)    You may use the traditional method based on a table of random numbers.

(b)   You may use any other method for random sampling as long as it meets these two criteria:

(1)   sampling under the method is random. 

(2)   sampling under the method is without replacement.  Without replacement means that the method will not select the same service unit more than once.

§ 63.05 – What is a table of random numbers?

(a)    It is a list of integers whose frequency and sequence of appearance in the list have been determined entirely by chance. 

(b)   For convenience and simplicity in use, published tables of random numbers usually appear in the form of separate columns of five-digit numbers.  Both rows and columns may be consecutively numbered for easy reference.  Table 63.01 shows an example.

(c)    Appendix 98 is a comprehensive table of random numbers you may use for random sampling if you choose to use this method.

Table 63.01. Example of a Table of Random Numbers

Rows

(1)

(2)

(3)

(4)

(5)

1

10480

15011

01$536

02011

81647

2

22368

46573

25595

85393

30995

3

24130

48360

22527

97265

76393

4

42167

93093

06243

61680

07856

5

37570

39975

81837

16656

06121

§ 63.07 – What is the list of all service units that I expect to operate?

 

(a)    It is the amount of revenue service that you expect to operate. 

(b)   It is measured with the following characteristics:

(1)   It is in the unit of sampling and measurement of the sampling plan you have chosen.

(2)   It is for the duration corresponding to the sampling frequency that you have chosen for your sampling plan.  The duration would be a day for interval-based sampling but a week, a month, or a quarter for period-based sampling.

(3)   It is for each of the service groups you have defined if your sampling plan is based on service grouping.

(c)    For scheduled services, the list must include:

(1)   all service units that are listed on the schedule, and

(2)   all service units that are not on the schedule but are expected to be operated, such as trippers, shuttles, and other special operations.

(d)   It would be the number of one-way bus trips you expect to operate in a week by your MB express routes, for example, if:

(1)   your sampling plan is in terms of one-way bus trips,

(2)   you have chosen weekly sampling for your MB service,

(3)   your sampling plan involves service grouping, and

(4)   you use express routes as one of the groups.

§ 63.09 – How do I develop the list of all service units for using a table of random numbers?

(a)    Suppose that:

(1)   you have chosen weekly sampling for your vanpool service,

(2)   your sampling plan requires 2 vanpool-days per week,

(3)   you want to select a random sample for next week, and

(4)   you have 101 vanpools and each of them is expected to operate every day next week.

(b)   One way to develop the list would be to assign a serial number of four-digits to each vanpool-day for all 707 combinations of vanpools and service days.  The first digit would represent the day of week with 1 for Monday and 7 for Sunday.  The other three digits would represent vanpool numbers ranging from 001 through 101.

(c)    The vanpool numbers may differ from what you use for your internal purposes.  Make sure that you have a one-to-one list between the internal vanpool numbers and the new serial numbers if they differ.

(d)   The serial numbers on a given day must be consecutive without any gaps.

(e)    Write down just the first and the last for each day of week so that you will know the range of numbers.  For example, the range for Monday is 1001-1101.

(f)    You should summarize these serial numbers in a summary table as in Table 63.03.

Table 63.03.  Example of a Summary Table of Serial Numbers

Day of Week

Range of Serial Numbers

1 (Monday)

1001-1101

2

2001-2101

3

3001-3101

4

4001-4101

5

5001-5101

6

6001-6101

7

7001-7101

§ 63.11 – How do I use a table of random numbers?

 

(a)    Suppose that:

(1)   you have 101 vanpools that you expect to operate every day of next week,

(2)   you have numbered the vanpool days for all vanpools as shown in Table 63.03, and

(3)   your sampling plan for your vanpool service requires 2 vanpool days per week. 

(b)   You must work with a constant length of digits from a table of random numbers for sampling.  This constant length is given by the number of digits in the longest serial number you have assigned to members of the list of all service units. 

(1)   This constant length would be 4 for the example in Table 63.03 because all serial numbers are four-digits long. 

(2)   This constant length would be 5 if your serial numbers vary in length, ranging from one to five digits.

(c)    You must combine adjacent digits from the table of random numbers as needed to obtain a two-, three-, or four-digit number, or any other length number from the table. 

(1)   You may choose to work with rows or columns in combining adjacent digits.  You may start with any row if you choose to work with rows.  You may start with any column if you choose to work with columns.  You may also choose to work from right to left or from left to right if you choose to work with rows. 

(2)   If you choose to work with rows and to start with row 1, for example, the first 9 four-digit numbers from Table 63.01 would be:

 

1048, 0480, 4801, 8015, 0150, 1501, 5011, 0110, and 1101.

 

(d)   You must continue forming four-digit numbers until you find two four-digit numbers from the table of random numbers that are in the summary table of serial numbers (Table 63.03).  In the above example, these two numbers are 1048 and 1101.  That is, you should select vanpools 48 and 101 and collect sample data from them on Monday of next week.

(e)    Once you are done sampling for a week, you should mark where you stopped forming four-digit numbers in the table of random numbers.  For example, the symbol, $, has been inserted between digits 1 and 5 in row 1 and column 3 of Table 63.01.  You should start the above process for a later week after that mark.

(f)    Once you are done sampling for a year, you should mark where you stopped forming four-digit numbers in the table of random numbers if you plan to use this method of random sampling in the future.  

(1)   If you number your service units exactly as for a previous sampling year, you should start the above process for a new sampling year after the last mark of your previous sampling year.

(2)   If you number your service units with a different approach for a new sampling year, you may start the above process anywhere in the table of random numbers.

§ 63.13 – What are the pros and cons of using a table of random numbers?

 

(a)    Using a table of random numbers for random sampling has the following advantages:

(1)   It is applicable to all situations.

(2)   You do not need to list explicitly all service units.

(b)   It has the following disadvantages:

(1)   You must number your service units consecutively without gaps, at least within each subset of your service units.  Subsets are formed by route, type of service days, etc.

(2)   You may not be able to take advantage of the serial numbers you have already assigned to your service units for internal purposes.

(3)   It can be difficult to use if the serial numbers have a large number of digits.

§ 63.15 – What information should I keep from my sampling process?

 

(a)    You should have an auditable record of your sampling process.  That record should cover the following:

(1)   A written description of the sampling plan.

(2)   A written procedure for your method of selecting a sample at random.

(3)   The list of all service units from which you selected a sample at random for each act of sampling.  For example, you should have 52 such lists if you did weekly sampling for an entire year.

(4)   The random sample.

§ 65.01 – What method may I use to collect the sample data?

(a)    One common method involves one or more ride checkers observing and recording passenger activities while riding in a transit vehicle. 

(b)   An increasingly common method uses APCs to record passenger activities instead. 

(c)    You may use one of these or any other method to collect the data from each service unit of your random sample as long as your method meets these criteria:

(1)   it obtains data from direct measurement or direct observation without passenger intercept,

(2)   it provides data you must have to determine PMT for each service unit, and

(3)   it meets the requirements on measurement accuracy in the NTD Reporting Manual.

§ 65.03 – What approach may I use to determine PMT for each service unit of my sample?

(a)    You may use the load-based approach.  It determines PMT by multiplying the number of passengers onboard a transit vehicle between each pair of consecutive stops by the distance between these stops.

(b)   You may also use the distance-based approach.  It determines PMT by keeping track of the distance traveled by each passenger carried by a service unit of your random sample.

§ 65.05 – What data items must I collect to use the load-based approach for scheduled services?

(a)    You must collect the required data items separately for each one-way vehicle trip in your service unit. 

(1)   If your service unit is a round-trip bus trip, for example, it has two one-way vehicle trips. 

(2)   If a service unit is a one-way train trip with three passenger cars, for example, it has three one-way vehicle trips.

(b)   The following data items are required for each one-way vehicle trip:

(1)   the number of people who boarded at each stop,

(2)   the number of people who alighted at each stop,

(3)   the distance between any pair of consecutive stops at which boardings or alightings occurred,

(4)   the number of people onboard the vehicle between any pair of consecutive stops,

(5)   the number of people who stayed on from the previous one-way vehicle trip, and

(6)   the number of people who remained on the vehicle at the last stop.

§ 65.07 – What data must I collect to use the load-based approach for non-scheduled services?

(a)    For commuter vanpool, the following data items are required for each direction of commuting:

(1)   the number of people who boarded at each pick-up location,

(2)   the number of people who alighted at each drop-off location, and

(3)   the distance between any pair of consecutive stops at which pick-up or drop-off occurred.

(b)   For demand response (DR and DT), you must collect the required data items continuously during the entire vehicle day sampled:

(1)   the odometer reading at each pick-up location,

(2)   the number of people onboard between each pair of consecutive locations at which pick-up or drop-off occurred, and

(3)   the odometer reading at each drop-off location.

(c)    You should treat non-commuter vanpool as demand response for data collection. 

§ 65.09 – How should I determine between-stop distances for the load-based approach?

(a)    You should avoid using maps to estimate between-stop distances under all circumstances.

(b)   For services without designated stops, including demand response (DR and DT), jitney (JT), vanpool (VP), or fixed-route services without designated stops:

(1)   If available, you should always use the onboard odometer to determine the between-stop distances for each service unit in your random sample.  You should make sure that the vehicles for the sampled service unit have a working odometer onboard before they start for the sampled service unit.

(2)   If your vehicle does not have an onboard odometer, you should determine the distance by retracing the path and the stops by automobile.

(3)   You should record your odometer readings at least to one-tenth of a mile.

(c)    For ferryboat (FB), aerial tramway (TR) and all rail services, you may want to predetermine the between-station distances for all routes and directions.

(d)   For fixed-route services with designated stops, you should use one of two approaches:

(1)   predetermine the between-stop distances for all routes and directions, or

(2)   record the onboard odometer readings at individual stops.

(e)    You may use different methods to predetermine the between-stop distances:

(1)   use an up-to-date GIS of your network of routes and stops, or

(2)   record the odometer readings while you drive through all of your routes and related deviations and directions.

(f)    If you predetermine between-stop distances, you must keep them updated to reflect any changes in your services.

§ 65.11 – What additional data should I collect to identify each service unit of my sample?

 

(a)    You must record the date and the type of service days for all cases. 

(b)   For commuter rail (CR), heavy rail (HR), and light rail (LR), you must also record the weekday time period that you will be reporting to the NTD for weekdays.

(c)    If your sampling plan is based on the PPMT option, you must record route identification.

(d)   If your sampling plan is based on service grouping, you should also record information that is necessary to determine group membership of each service unit in the random sample.

§ 65.13 – When do I use the different approaches to determining PMT?

(a)    The load-based approach is applicable to all circumstances.  Under conditions of heavy loads or high boarding volumes, however, extra care must be taken to maintain the required level of measurement accuracy.

(b)   The distance-based approach is useful under several circumstances.  For examples:

(1)   All passengers board and alight at the same locations, such as inclined plane (IP), aerial tramway (TR), and most ferryboat (FB) operations.

(2)   Services with a small number of passengers who board and alight at a small number of stops, such as demand response (DR and DT).

(3)   Services with a small number of frequent passengers who board and alight at a small number of stops, such as commuter vanpool.

(4)   Any service with a ticketing system that keeps track of the origin and destination for every boarding with a known distance.

§ 65.15 – What instrument should I use to collect the data for the distance-based approach?

(a)    You may use any instrument that you have designed as long as you can use it to record the required data items correctly.

(b)   If you use human ride checkers, the instrument may be a piece of paper and a pencil or it may be a hand-held device.

(c)    Appendix 92 provides an example of both blank and filled-out paper instruments for the distance-based approach.

§ 65.17 – What instrument should I use to collect data for the load-based approach?

(a)    You may use any instrument that you have designed as long as you can record the required data items correctly.

(b)   If you use APCs, the instrument would be computer software and hardware that records the counts and other data items transmitted from the APCs.

(c)    If you use human ride checkers, the instrument may be a piece of paper and a pencil or it may be a hand-held device.

(d)   If you use a hand-held device, it is critical that the unit accepts counts of boardings and alightings that may not be equal for a one-way vehicle trip.

(e)    The instrument you design may take slightly different formats for different services.  Three examples of blank and filled-out instruments are shown as appendices:

(1)   demand response – Appendix 93.

(2)   commuter vanpool – Appendix 94.

(3)   fixed-route services – Appendix 95.

(f)    If you are going to use one of these example instruments, you should study it carefully before reading the following guidance.

§ 65.19 – What pre-survey procedures should I follow if I use a paper instrument and human ride checkers?

(a)    You should use an appropriate survey sheet for each service unit selected in the sample.  This survey sheet may be one of those from the appendices or one that you have designed, but it is important that you select a survey sheet that is designed for the service to be surveyed.

(b)   For non-scheduled services, including demand response (DR and DT) and vanpool (VP), a survey sheet should be used for each driver of the survey vehicle during an entire day.

(c)    For scheduled services, a survey sheet should be used for each one-way vehicle trip of your service unit that you have chosen for your sampling plan.

(d)   The ride checker(s) should carry several extra survey sheets in the event that extra sheets are needed.

(e)    You should learn about the likely load and boarding volumes for each service unit to be surveyed. 

(1)   You may need to use more than one ride checker under conditions of high loads and high boarding volumes. 

(2)   If more than one ride checker is used, the separate survey sheets should also be labeled with the door(s) that each ride checker is responsible for.

(f)    If you rely on the onboard odometer to determine the between-stop distances, make sure that it works properly.  If you cannot fix a malfunctioning odometer in time for a ride check, use a different vehicle with a working odometer. 

(g)   Before going into the field, the survey supervisor should fill in the data items that identify the service unit to be surveyed.  If your service unit has more than one one-way vehicle trip, identify each one-way vehicle trip separately.

(h)   If you rely on predetermined between-stop distances, the survey supervisor should also use the survey sheet(s) in Appendix 95 to:

(1)   Fill in the stop numbers in column (7) and stop descriptions in column (8) for all stops.

(2)   Cross out column (9) to avoid confusion in the field.

(i)     You should write the page numbers in the box in the lower right-hand corner of each survey sheet if you use more than one survey sheet for a given one-way vehicle trip.

§ 65.21 – What manual survey procedures should I follow for demand response (DR and DT) with the distance-based approach?

(a)    You may use the survey sheet for the distance-based approach in Appendix 92.

(b)   You must record individual trips by each pair of origin and destination.  The filled-out form in Appendix 92 illustrates three cases of pick-up and drop-off patterns:

(1)   The first pick-up illustrates the “one origin-many destinations” case.  The driver picked up 16 passengers at 1020 J Street.  He immediately distributed these passengers according to their three drop-off destinations under item (8). 

(2)   The second pick-up illustrates the “one origin-one destination” case.  At the next pick-up address, 506 10th Street, 17 passengers boarded and all were driven to the same destination.  Here, a single line records all the necessary information.

(3)   The last two pick-ups illustrate a “many origins-one destination” case.  Here, the driver records the pick-up addresses and repeats the destinations; that is, he handles each as an individual trip.

(c)    You must record the odometer readings for each pick-up and drop-off.

(1)   Item (7), “Pick-Up Odometer Reading,” should be recorded immediately upon picking up the passenger(s). 

(2)   Item (8), “Drop-Off Odometer Reading,” should be recorded immediately upon dropping off the passengers. 

(3)   You should also record the odometer readings to at least one-tenth of a mile when the odometer allows.

(d)   You should use additional pages if a service unit involves more stops than are given on a page.  You should write the page numbers in the box in the lower right-hand corner.

(e)    As an alternative to data recording by the driver, the driver can call in the information to the dispatcher if you have two-way radio communications on all vehicles.

(1)   When the driver arrives at a pick-up point, he can call in items (5)-(8).

(2)   When he arrives at each destination, he can call in item (9) and verify how many passengers were dropped off at that destination.

§ 65.23 – What manual survey procedures should I follow for demand response (DR and DT) with the load-based approach?

(a)    You may use the survey sheet for the load-based approach for demand response in Appendix 93.

(b)   For each pick-up or drop-off, you must record the following:

(1)   whether it is a pick-up or drop-off in column (5),

(2)   a description of the location in column (6),

(3)   the odometer reading in column (7), and

(4)   the leaving load in column (8).

(c)    The filled-out form in Appendix 93 shows the recorded information for the example shown in Appendix 92.  The leaving load at the last drop-off location should be 0.

(d)   You should record the odometer readings to at least one-tenth of a mile.

(e)    You should use additional pages if a service unit involves more stops than are given on a page.  You should write the page numbers in the box in the lower right-hand corner.

(f)    As an alternative to data recording by the driver, the driver can call in the information to the dispatcher if you have two-way radio communications on all vehicles.  Before leaving each pick-up or drop-off location, the driver can call in items (5)-(8).

§ 65.25 – What manual survey procedures should I follow for commuter vanpool with the load-based approach?

(a)    Suppose that you have chosen to sample on a monthly basis.

(b)   Before a new month starts, you should communicate with the driver of each sampled vanpool about the days on which he must collect sample data during the new month.

(c)    For each sampled vanpool day, the driver should fill in the identification data before he leaves home, including the date, the day of week, and the vanpool number. 

(d)   The driver is required to record the travel data, including the van odometer reading whenever any rider gets on or off the van along with the number of riders who get on the van and the number of riders who get off the van.  This recording is to be done separately for travel to work and travel from work.  The filled-out form in Appendix 94 shows the travel data for a vanpool of 6 riders with a round-trip-distance of 78 miles.  The driver picks up all 5 riders at a single location but drops them off at three different locations in the morning.  In the afternoon, the process reverses itself. 

(1)   Once the driver gets on the van in the morning, he should enter 1 in the ON column (6) and record the odometer reading at 29,366.0 in column (8). 

(2)   He then leaves for picking-up 5 fellow vanpoolers at another location.  Once they get on the van, he should enter 5 in (6), and record the odometer reading at 369.1 in (8) before departing that location.

(3)   At the first drop-off location, 3 vanpoolers get off.  Before leaving, the driver should enter 3 in the OFF column (7), and record the odometer reading at 395.3 in (8).

(4)   One vanpooler gets of the van at each of the next two drop-off locations.  Before leaving these locations, the driver should enter 1 in the OFF column, and record the odometer reading at 396.8 and 397.5, respectively. 

(5)   Finally, the driver arrives at his own destination.  Before he leaves the van, he should record the odometer reading again at 405.0.

(e)    The day after each sample day, you should communicate with each driver involved in collecting sample data to determine if he actually recorded the sample data.  Sample data may be not recorded for a variety of reasons. 

(1)   If the data were collected, the driver should send the filled-out survey sheet immediately,

(2)   If the driver forgot to collect the data, he should be asked to collect the data next day,

(3)   If the driver refused to collect the data or the vanpool has been terminated, a replacement vanpool day should be selected at random.

§ 65.27 – What instructions should I give my ride checkers if I do not use predetermined between-stop distances for fixed-route services?

(a)    Take enough copies of the survey sheet in Appendix 95 or an alternative sheet.

(b)   Use separate survey sheets for separate one-way vehicle trips if your service unit has more than one one-way vehicle trip.

(c)    Use additional survey sheets if needed for a given one-way trip.

(d)   Board the transit vehicle at the beginning point of the service unit and position yourself so that you can observe the doors for which you are responsible. 

(e)    Before the vehicle leaves the beginning point, record:

(1)   Stop #1 in column (7),

(2)   stop description of the beginning point in column (8),

(3)   odometer reading to at least one-tenth of a mile in column (9),

(4)   number of passengers who have stayed onboard from the last trip (13), and

(5)   number of passengers boarded in (10), including the passengers who have stayed onboard from the last trip in (e)(4).

(f)    When the vehicle leaves the beginning point, record the number of passengers onboard in column (12), including any passengers who have stayed onboard from the last trip.

(g)   Only at points where the vehicle stops during the service unit, record:

(1)   stop number in (7),

(2)   stop description in (8),

(3)   odometer reading (from the driver) in (9),

(4)   passengers boarded in (10), and

(5)   passengers alighted in (11).

(h)   Between stops, count the number of passengers on board (12).  You should record this number as the leaving load.  For example, between stops 2 and 3 you should record this number in the row for stop 2 rather than in the row for stop 3.

(i)     At the end point of each one-way trip, record the number of passengers who will stay on board to the next trip in column (14) and in column (11) as passengers alighted.

§ 65.29 – What steps should I take if I fail to collect the sample data from a particular unit?

(a)    You may fail to collect the required sample data from any particular unit in your sample:

(1)   The unit may be canceled for a variety of operational reasons.

(2)   The ride checker(s) may fail to show up for the unit.

(3)   The ride checker(s) may fail to collect the data.

(b)   You must replace the missed unit as soon as possible on the same type of service days.

(c)    For period-based sampling:

(1)   If the rest of the sampling period (a week, a month, or a quarter) has at least one service day of the same type as the missed service unit, select one service unit from the next service day of the same type.  For example, if the missed service unit is on the second Monday of a month and your sampling is monthly, you should get a replacement unit from the third Monday of the month.

(2)   If the rest of the sampling period does not have any service day of the same type left, select one service unit from the first service day of the same type during the next sampling period.  For example, if the missed service unit is on a Monday and your sampling is weekly, you should get a replacement unit from the next Monday. 

(d)   For interval-based sampling:

(1)   If the rest of the report year has at least one service day of the same type as the missed service unit, select one service unit from the next service day of the same type.

(2)   If the rest of the report year does not have any service day of the same type left, select one service unit from the next day of service.

(e)    The replacement unit must be selected at random in all cases.

§ 67.01 – What steps should I take after I have collected the sample data?

(a)    Design a format for recording your sample data.

(b)   Enter the raw data.

(c)    Process the entered data.

(d)   Identify errors in the entered data.

(e)    Identify sources of the data errors, if any.

(f)    Correct the data errors, if any.

(g)   What you should do within each step depends on your situation.  To be specific, the following example is used for the rest of this subsection:

(1)   you collect sample data with human ride checkers from one-way bus trips with designated stops,

(2)   you use the load-based approach to determining PMT,

(3)   you use predetermined between-stop distances, and

(4)   you have collected sample data from a route whose longest one-way trip is 4 miles.

§ 67.03 – What should I consider in designing the format for data recording?

(a)    The data items you have collected to determine PMT.  The exact data items depend on your service and the approach you have taken to determine PMT.

(b)   The data items that identify the service units in your sample.

(c)    A format that is easy for data analysis.

(d)   Suppose that you have designed a format in Table 67.01.  With this format, you enter the field data (7)-(14) as they appear on the field survey sheet shown in the filled-out form in Appendix 95.  Item (8) is not shown due to space limit.  The identification data items at the top of the survey sheet (1)-(6) are repeated for each stop of this one-way trip.

Table 67.01.  Example Format for Data Recording

Date

Day of Week

Time Period

Route No.

Trip No.

Direction

Stop Sequence

Distance to Next Stop

No. of Pass. Boarded

No. of Pass. Alighted

No. of Pass. On Board (Leaving Load)

No. of Pass. from Previous Trip (Stop 1 only)

No. of Pass. Continuing to Next Trip (Last Stop only)

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(9)

(10)

(11)

(12)

(13)

(14)

10/13/05

Thur

Midday

11

408

Outbound

1

0.3

20

0

20

2

 

10/13/05

Thur

Midday

11

408

Outbound

2

0.7

2

1

21

 

 

10/13/05

Thur

Midday

11

408

Outbound

3

0.6

0

2

19

 

 

10/13/05

Thur

Midday

11

408

Outbound

4

0.3

1

3

17

 

 

10/13/05

Thur

Midday

11

408

Outbound

5

0.5

1

10

8

 

 

10/13/05

Thur

Midday

11

408

Outbound

6

0.8

0

2

6

 

 

10/13/05

Thur

Midday

11

408

Outbound

7

0.2

0

1

5

 

 

10/13/05

Thur

Midday

11

408

Outbound

8

0.1

0

2

3

 

 

10/13/05

Thur

Midday

11

408

Outbound

9

0.1

0

2

1

 

 

10/13/05

Thur

Midday

11

408

Outbound

10

0.3

0

0

1

 

 

10/13/05

Thur

Midday

11

408

Outbound

11

0.1

0

0

1

 

 

10/13/05

Thur

Midday

11

408

Outbound

12

0.0

0

1

1

 

1

§ 67.05 – When should I enter my sample data?

(a)    You should have the sample data from each service unit entered immediately after your ride checker(s) has come back from the field.

(b)   This has a number of advantages:

(1)   reducing the chance of loss of information,

(2)   increasing the chance of correcting data errors, if any,

(3)   being ready to use the cumulative sample data any time during the sampling year, and

(4)   minimizing the rush at the end of the year.

§ 67.07 – How should I process the entered data?

(a)    You should process the data as follows immediately after you have entered them.  If your service unit has more than one one-way vehicle trip, you should process the data for individual one-way vehicle trips:

(1)   Sum the number of passengers boarded at individual stops in column (10) of Table 67.01 to get the total number of passengers boarded (UPT).  It is 24 in this case.

(2)   Sum the number of passengers alighted at individual stops in column (11) of Table 67.01 to get the total number of passengers alighted.  It is 24 in this case.

(3)   Calculate the load between every pair of two consecutive stops.  Table 67.03 shows an example and the formulas for calculating leaving loads and arriving loads.

(4)   Calculate PMT for each pair of consecutive stops by multiplying the calculated load with the between-stop distance.  Table 67.03 also shows the calculation of PMT with both leaving loads and arriving loads.

(5)   Calculate total PMT.  It is 47.8 miles in this case.

(6)   Divide total PMT by the total number of passengers boarded to get APTL.  It is 1.99 miles in this case.

(7)   Calculate vehicle trip length by summing up the predetermined between-stop distances in column (9).  It is 4.0 miles in this case.

(b)   If your sampling plan is based on the PPMT option, you should also process the data as follows immediately to calculate the ratio of PMT to PPMT for each service unit:

(1)   Calculate the average route length for each route.

(2)   Calculate PPMT by multiplying UPT by average route length.

(3)   Divide PMT by PPMT to get the ratio for each service unit.

(4)   Follow Subsection 85 on calculating average route length and PPMT.

Table 67.03.  Calculation of Loads and PMT

Load Type

Stop Sequence

Distance to Next Stop

No. of Pass. Boarded

No. of Pass. Alighted

No. of Pass. from Previous Trip

Calculated Load

PMT

Leaving Load

1

0.3

20

0

2

20

6.0

2

0.7

2

1

 

21

14.7

3

0.6

0

2

 

19

11.4

4

0.3

1

3

 

17

5.1

5

0.5

1

10

 

8

4.0

6

0.8

0

2

 

6

4.8

7

0.2

0

1

 

5

1.0

8

0.1

0

2

 

3

0.3

9

0.1

0

2

 

1

0.1

10

0.3

0

0

 

1

0.3

11

0.1

0

0

 

1

0.1

12

0.0

0

1

 

0

0.0

Total

4.0

24

24

2

N/A

47.8

Load for Stop 1 =

Current Boarding

 

Load for Other Stops =

Previous Load + Current Boarding – Current Alighting

Arriving Load

Stop Sequence

Distance from Previous Stop

No. of Pass. Boarded

No. of Pass. Alighted

No. of Pass. from Previous Trip

Calculated Load

PMT

1

0.0

20

0

2

0

0.0

2

0.3

2

1

 

20

6.0

3

0.7

0

2

 

21

14.7

4

0.6

1

3

 

19

11.4

5

0.3

1

10

 

17

5.1

6

0.5

0

2

 

8

4.0

7

0.8

0

1

 

6

4.8

8

0.2

0

2

 

5

1.0

9

0.1

0

2

 

3

0.3

10

0.1

0

0

 

1

0.1

11

0.3

0

0

 

1

0.3

12

0.1

0

1

 

1

0.1

Total

4.0

24

24

2

N/A

47.8

Load for Stop 1 =

0

 

 

 

 

Load for Other Stops =

Previous Load + Previous Boarding – Previous Alighting

§ 67.09 – How may I use the processed data to identify potential errors in the sample data?

(a)    Make sure that UPT and PMT are consistent for each service unit in the sample.  For example, they should both be zero or both be positive. 

(b)   Compare vehicle trip length with the longest actual length of the route.  Vehicle trip length must not exceed the longest route length.

(c)    Compare APTL with vehicle trip length and route length.  APTL must not exceed either.

(d)   Compare the total number of passengers boarded with the total number of passengers alighted.  They must be equal.

(e)    Examine the calculated load at the end point of the trip.  It must be zero for leaving loads.

(f)    If calculated, examine the PMT to PPMT ratio for each service unit.  It must not exceed 1.

§ 67.11 – How do I identify the sources of any errors?

(a)    If you have identified any error from the previous step, you should start with the calculations you did in processing the sample data to determine if an error is a calculation error or an error in the sample data.

(b)   Check if you have correctly calculated loads, UPT, PMT, and APTL.

(c)    Check if you have used between-stop distances and loads consistently:

(1)   If you use leaving loads, you must use the distance to the next stop.  The distance should be zero for the ending point of a one-way trip.

(2)   If you use arriving loads, you must use the distance from the previous stop.  The distance should be zero for the beginning point of a trip. 

(d)   Check the predetermined between-stop distances you entered.

(e)    Compare your calculated load with the observed load from the field.

§ 67.13 – How do I correct any errors?

(a)    Table 67.05 shows an example of sample data for a one-way trip where PMT is based on calculated leaving loads.  The first row of Table 67.07 shows the vehicle trip length, UPT, PMT, APTL, and the ratio of PMT/PPMT for this trip.

(b)   It has the following errors:

(1)   Vehicle trip length > route length.

(2)   APTL > route length.

(3)   Total boardings in column (10) < total alightings in column (11).

(4)   The load at the end stop < 0.

(c)    Error (b)(1) clearly indicates errors in the predetermined between-stop distances.  If you check what you have entered in column (9), you would notice the 7 miles from stop 3 to stop 4.  Correct the data-entry error by replacing 7 by 0.7.  After this change,

(1)   vehicle trip length matches the route length,

(2)   APTL becomes smaller than the route length, and

(3)   PMT is reduced to 34.7 with an APTL of 1.58 miles. 

(d)   To identify the source of error (3), compare the calculated loads with the observed loads.  You may notice that the calculated load is lower by 2 at the first stop.  It appears that the ride checker did not include the number of passengers from the previous trip in the number of boardings at the first stop.  With this correction,

(1)   Boardings become greater than alightings.

(2)   PMT is increased to 42.7 miles with an APTL of 1.78 miles.

Table 67.05.  Example of Correcting Data Errors

Stop Sequence

Distance to Next Stop

No. of Pass. Boarded

No. of Pass. Alighted

Observed Leaving Load

No. of Pass. from Previous Trip (Stop 1 only)

No. of Pass. Continuing to Next Trip (Last Stop only)

Calculated Leaving Load

PMT

(7)

(9)

(10)

(11)

(12)

(13)

(14)

(15)

(16)

1

0.0

18

0

20

2

 

18

0.0

2

0.3

2

1

21

 

 

19

5.7

3

7.0

0

2

19

 

 

17

119.0

4

0.6

1

3

17

 

 

15

9.0

5

0.3

1

9

8

 

 

7

2.1

6

0.5

0

2

6

 

 

5

2.5

7

0.8

0

1

5

 

 

4

3.2

8

0.2

0

2

3

 

 

2

0.4

9

0.1

0

2

1

 

 

0

0.0

10

0.1

0

0

1

 

 

0

0.0

11

0.3

0

0

1

 

 

0

0.0

12

0.1

0

1

1

 

1

-1

-0.1

Total

10.3

22

23

 

2

1

N/A

141.8

(e)    To identify why boardings are still larger than alightings, compare the recalculated loads with the observed loads again.  You may notice that the recalculated load starts deviating from the observed load at stop 5.  Since the calculated load is one passenger too big, increase the number of alighted passengers at stop 5 by 1 from 9 to 10.  With this correction,

(1)   Boardings equal alightings,

(2)   The leaving load at the end stop is 0, and

(3)   PMT is further reduced to 40.3 with an APTL of 1.68 miles.

(f)    You should also check the consistency between between-stop distances and the calculated loads.  Column (9) is based on the distance from the previous stop, but the calculated load is the leaving load.  Correcting this error leads to a final PMT of 47.8 with an APTL of 1.99 miles.

(g)   Table 67.07 also shows vehicle trip distance, UPT, PMT, APTL, and ratio PMT/PPMT for the cumulative corrections in (c), (d), (e), and (f).      

Table 67.07.  Impacts of Correcting Errors

Error Corrections

Vehicle Trip Length

PMT

UPT

APTL

PMT/PPMT

No corrections

10.3

141.8

22

6.45

0.63

§69.13 (c)

4.0

34.7

22

1.58

0.39

§69.13 (c) + (d)

4.0

42.7

24

1.78

0.44

§69.13 (c) + (d) + (e)

4.0

40.3

24

1.68

0.42

§69.13 (c) + (d) + (e) + (f)

4.0

47.8

24

1.99

0.50

§ 67.15 – What should I do if I fail to correct the data errors for a particular service unit?

(a)    You should treat the service unit as if it were missed for data collection.

(b)   You should follow the guidance in §65.29 for getting a replacement unit.

§ 67.17 – What steps should I take after I have identified and corrected errors in my data?

(a)    You should stack the corrected sample data from the field as shown in Table 67.01 in one or more worksheets.  These worksheets along with the survey sheets become an auditable record of your sample data.

(b)   You should enter the summary data at the level of your unit of sampling and measurement in a separate worksheet.  These summary data are ready for developing new sampling plans or for estimating service-consumed data for the NTD.

(c)    Table 67.09 shows how that summary worksheet looks with the column headings and the summary sample data for one service unit.

Table 67.09.  Example of Summary Sample Data

Date

Day of Week

Time Period

Route No.

Trip No.

Direction

Vehicle Trip Length

UPT

PMT

(1)

(2)

(3)

(4)

(5)

(6)

 

 

 

10/13/05

Thur

Midday

11

408

Outbound

4.0

24

47.8