(a) All four efficiency options are available for period-based sampling. Only the first two are available for interval-based sampling.

(b) The base option is available to you if you have data on PMT from your sample. But it is not recommended in most cases if a 100% count of annual UPT is available and reliable.

(c) The APTL option is available to you if you meet the following two criteria:

(1) you are going to report a 100% count of annual UPT, and

(2) you have data on both UPT and PMT from your sample data.

(d) The PPMT option is available to you if you meet all of the following criteria:

(1) you are going to report a 100% count of annual UPT,

(2) you have data on both UPT and PMT from your sample data,

(3) your service is a fixed-route service,

(4) you have your 100% count of annual UPT for each route, and

(5) you have data on annual total vehicle revenue miles and annual total vehicle revenue one-way trips for each route.

(e) The grouping option is available to you as long as you have some basis for dividing your service into two or more groups.