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51 CHAPTER 7 Tools for Analyzing Crowding Crowding is important to passengers for their comfort; to with 36 transverse seats, 6 longitudinal seats, a stairwell for the operations, because it can slow the boarding and alighting rear door, and 6 ft of unused length at the front of the bus. (For process; and to planning, as a measure of efficiency. These dif- greater detail, the TCQSM's LOS F has been subdivided into ferent viewpoints need different measures derived from pas- levels F1 and F2.) senger count data. However, while these thresholds account well for passenger The planning viewpoint is concerned with average load at comfort levels on an individual trip, they do not mean much the peak volume point, that is, the segment whose average when applied to an "average trip." Neither operations nor pas- load is the greatest. Schedule planning often uses peak point sengers care much about average crowding. What really mat- load to determine headway, using a nominal design capacity. ters is the distribution of crowding and, in particular, extreme Because this measure is a single number that is widely under- values. Because of the large sample sizes afforded by APC data, stood, it is not covered further. However, impacts on opera- analysts can derive, from maximum load observations, distri- tions and on passengers are strongly affected by the random butions of both trips and passengers by crowding level. distribution of passenger crowding, something that can only To illustrate, the researchers analyzed 30 observations of be analyzed well with the large samples that APCs can afford. peak-hour trips on a certain route and found that the mean This chapter describes methods for analyzing passenger value of maximum load was 40.3. (The data and analysis crowding. These methods have been programmed as proto- described in this chapter can be found in the spreadsheet file types in a spreadsheet file which is available on the project on the project description web page for TCRP Project H-28 description web page for TCRP Project H-28 on the TRB on the TRB website: www.trb.org.) With the example 42-seat website: www.trb.org. buses, the TCQSM would rate this route-period in LOS C. On average, load is less than the number of seats, which deceptively 7.1 Distribution of Crowding suggests that everybody should get a seat and that there should by Bus Trip be little problem of crowding interfering with boarding and alighting. In fact, the distribution of maximum load over those For both the passenger and operations viewpoints, load can 30 trips, shown in Figure 17, offers quite a different picture. be examined on every segment of a trip. However, for most About 47% of the trips had standees (load > 42); and 20% of purposes, analysts want to focus on the most crowded segment the trips were either "crowded" or "overcrowded" (load > 62), (the maximum load segment) of each trip. which could seriously affect running time. Yet, 27% of the The maximum load segment of any trip may differ from the observed trips had at least half their bus seats empty, suggest- route's peak volume point. If averaged over many trips, the aver- ing a possible bunching problem. age maximum load will often be greater, and cannot be smaller, than average load at the peak volume point. Average maximum load is a measure suggested by the 7.2 Distribution of Crowding Transit Capacity and Quality of Service Manual (TCQSM) to Experience by Passenger characterize level of service with respect to crowding (27). The 7.2.1 Classification of Crowding Experience TCQSM defines six levels of service (LOSs) (A through F) and suggests thresholds based on the number of seats and amount Measures of passenger service quality should use passen- of available standing space per standee. The examples in this gers, not bus trips, as units and should adopt the passenger's section use the thresholds shown in Table 8; they were deter- viewpoint. Crowding experience from the passenger's view- mined using TCQSM default values and assuming a 40-ft bus point can be classified as follows:

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52 Table 8. Example crowding thresholds. Load Basis Passenger Comfort TCQSM LOS (pax) 21 0.5 * (no. of seats) Can sit next to unoccupied seat A 32 0.75 * (no. of seats) Can choose seat B 42 no. of seats Seated C 53 3.85 sq. ft. per standee Standing but not crowded D 62 2.2 sq. ft. per standee Full E 69 1.6 sq. ft. per standee Borderline of crowded and overcrowded F1 LOS F from theTCQSM has been subdivided into levels F1 and F2. Seated next to an empty seat (corresponds to LOS A) ferent passenger experience is compared to the "experience" of Seated but not next to an empty seat (corresponds to the buses. While 6.7% of the buses were "overcrowded," only LOS B-C) 4.6% of the passengers were overcrowded standees--because Standing but not crowded (3.85 sq. ft. or more per standee; more than half the passengers on the crowded buses were for this example, load is no more than 53) (corresponds to seated. Very few passengers fall into the category "standing but LOS D) not crowded" because even though 17% of the buses had loads Standing and bus is full (2.2 to 3.85 sq. ft. per standee; for in this category, only a few of the passengers on those buses this example, load is between 54 and 62) (corresponds to were standing. And while 27% of the buses were in the least LOS E) crowded category, only 14% of the passengers are in that cate- Standing and crowded (1.6 to 2.2 sq. ft. per standee; for gory, because not many passengers were on those buses. this example, load is between 62 and 69) (corresponds to Distribution by passenger (rather than by trip) better indi- LOS F1) cates the level of service that passengers experience. For exam- Standing and overcrowded (less than 1.6 sq. ft. per standee) ple, Figure 18 shows that 14% of the passengers had excellent (corresponds to LOS F2) service (during peak hour, they were able to sit with an empty seat next to them); and the vast majority had service equiva- In this classification, if a bus with 42 seats has 70 passen- lent to a carpool (a seat next to an occupied seat). However, gers, then 42 passengers will be classified as "seated but not about 5% experienced overcrowding as standees; they are the next to an empty seat" (they experience LOS B-C); the other passengers who are likely to complain. 28 will be classified as "standing and overcrowded" (they expe- A distribution of passengers by experienced crowding can rience LOS F2). be used to support a service quality standard such as When all the passengers on the 30 trips used in the previ- ous example are classified, their distribution is as shown in "During peak periods, at least 80% of our customers should Figure 18. A comparison of Figures 17 and 18 shows how dif- be seated at the maximum load point, and 100% 100% Load more than 69 Standing, load > 69 90% 90% 80% Load up to 69 80% Standing, load up to 69 70% 70% Load up to 62 60% Standing, load up to 62 60% 50% Load up to 53 50% 40% Standing, load up to 53 Load up to 42 40% 30% 30% 20% Load up to 32 Seated next to occupied 20% seat 10% Load up to 21 10% Seated next to empty 0% seat mean = 40.3 0% Figure 17. Distribution of trips by Figure 18. Distribution of passengers maximum load. by crowding experience.

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53 "Fewer than 2% of our customers should have to stand on This formula is incorporated in the spreadsheet file that ana- an overcrowded bus (a bus with less than 1.6 sq. ft. stand- lyzes crowding. (The spreadsheet is available on the project ing space per person)." description web page for Project H-28 on the TRB website: www.trb.org.) This standard is much more customer oriented than, for Of course, the assumptions about where passengers sit or example, specifying that average load factor (load divided by stand are sometimes violated; some passengers choose to number of seats) not exceed 1.2. The latter is a common format stand when seats are available, and friends often choose to sit for load standards. However, passenger experience of crowding together, even if a bus is nearly empty. In such cases, however, is not based on average load, but is sensitive to extremes; fur- the service received by those passengers is still appropriately thermore, even on crowded trips, passenger experience is very classified based on the assumptions, because they had the different depending on whether one has a seat. option of sitting, or of sitting next to an empty seat, but chose something that they apparently preferred. 7.2.2 Assumptions About Seated Passengers Passenger counts do not provide direct observation of how many passengers are seated or whether they are next to an 7.2.3 Alternative Classifications empty seat. However, those figures can be estimated to a rea- Differentiating seated passengers depending on whether a sonable level of accuracy using three assumptions: passengers seat next to them is empty may be considered excessive detail. sit if they can, seats are in pairs (as is most often the case on Of course, the two classes of seated passengers can be col- buses), and passengers sit next to an empty seat if possible. lapsed. However, to the extent that market research shows Thus, for a bus with S seats and passenger load L, then that passengers like having an empty seat next to them, both If L S/2, everybody sits next to an empty seat; classes are worth measuring, particularly as these classes can If L S, nobody sits next to an empty seat; and be estimated using APC data. If L lies between S/2 and S, S - L passengers sit next to an For some purposes, all the passengers, seated and standing empty seat, because there are S - L empty seats. For exam- in a crowded bus, may be said to experience overcrowding. ple, if there are 42 seats and load is 32, 10 people sit next to This classification may be especially appropriate where the an empty seat and the other 22 people sit in pairs next to vehicle's ventilation system allows overcrowding to result in an occupied seat. unpleasant heat and odor.