§ 56.03 – Why do I need to consider revision?

(a)    Your service and the traveling habits of your customers change naturally over time.  

(b)   To meet certification requirements:

(1)   Such service and habit changes may increase the statistical variation in key quantities (e.g., PMT, APTL) and hence require larger sample sizes.

(2)   The sampling plans produced by this template are only certified to meet FTA’s requirements of 95% confidence with 10% precision for certain sampling cycles, presuming no major changes in your service.  

(3)   After this time, or after major changes in your service, a new template sampling plan must be developed to maintain certification of compliance with the FTA requirements.

(c)    To get more efficient sampling plans:

(1)   Such service and habit changes sometimes may reduce the statistical variation of key quantities (e.g., PMT, APTL).

(2)   You would be able to take advantage of such reduced variation by revising your template sampling plans using your most recent sample data that reflect these service and habit changes.

§ 56.05 – Under what conditions should I revise my template sampling plan?

(a)    If your next sampling year is your mandatory revising year, you must revise your template sampling plans.  Or

(b)   If you have made major changes to your service since you started using the current template sampling plan, you must consider revising your template sampling plan.

§ 56.07 – How do I know if next year is a mandatory revising year for me?

(a)    If you are required to sample every year, every 6th year is your mandatory revising year.  For example, if you used your 2010 NTD sample to develop a template sampling plan, report year 2016 is your mandatory revising year.

(b)   If you are required to sample every 3rd year, every 9th year is your mandatory revising year.  For example, if you used your 2010 NTD sample to develop a template sampling plan, report year 2019 is your mandatory revising year. 

(c)    Follow the Reporting Manual to determine whether you are required to sample every year.

§ 56.09 – What are considered major changes to my service?

(a)    A major change is any change you make to your service that is likely to lead to major changes in the statistical variation in a relevant quantity of your service. 

(b)   The relevant quantity of your service varies with the sampling options you choose.  It is PMT if you choose the base option, APTL if you choose the APTL option, etc.

(c)    The following are examples of a major change:

(1)   Making transfers fare-free for all passengers.

(2)   Adding or cutting express routes to the base of all local service.

(3)   Expanding or contracting your service by at least 25% in vehicle revenue miles.

(4)   Service restructuring that affects at least 25% of your service in vehicle revenue miles.

§ 56.11 – How do I determine if I must revise my template sampling plan after I have made major changes to my service?

(a)    Enter your sample from the current report year into the companion template as if you were going to develop a new template sampling plan. 

(1)   Enter your PPMT data if your current template sampling plan follows the PPMT option.

(2)   Enter the corresponding grouping data if your current template sampling plan follows the grouping option.

(b)   For period-based sampling, go to the PeriodPrecision Worksheet.  The index number you need depends on the efficiency option you have chosen for the current template sampling plan.  For example, you must use the value in cell D6 of Part A, Figure 56.01 (=32.7) if your template sampling plan is based on the APTL option with service grouping and if you have chosen to use your 100% UPT count by group in developing your annual estimates.

(c)    For interval-based sampling, go to the IntervalPrecision Worksheet.  The index number you need also depends on the efficiency option you have chosen for your current template sampling plan.  For example, you must use the value in cell C5 of Part B, Figure 56.01 (=31.3) if your template sampling plan is based on the APTL option.

(d)   You must revise your sampling plan if the precision index is smaller than 10.0.

A. PeriodPrecision Worksheet

B. IntervalPrecision Worksheet

Figure 56.01.  Layout of the PeriodPrecision and IntervalPrecision Worksheets