§ 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