When to Use School Trippers
School trippers are extra trips put out before and after school when the number of passengers attending the school is so high that the students would overwhelm the regularly scheduled service in the absence of trippers, especially in terms of causing pass-ups. While mostly used with schools, tripper service can be required at any location where a very large number of passengers need to arrive or leave the location at the same time.
Because of the school service rule , transit agencies must be sure that any school trippers they put out follow regularly scheduled routes and/or appear as regularly scheduled routes that the public can ride. SamTrans in San Mateo, CA and AC Transit in Oakland, CA are two transit agencies that have a large number of school service routes.
Because trippers require the use of a driver and a separate vehicle for a very short period of time - as little as twenty-minutes - they are very expensive to add, especially if the driver is working overtime, which is frequently the case. Adding a peak bus not only can result in bus shortages if there are not enough spares but adds additional cost in terms of prepping, servicing, and maintaining the vehicle. Because the total number of miles driven by a tripper is small, they usually are operated with older buses .
Do We Need to Add a Tripper?
In order to avoid adding trippers, we must employ strict passenger count requirements that regular service must meet in order to add one. Assuming the regular service schedule is optimized to meet the tripper trigger (the after school bell, for example), we measure the maximum load of the regular trip. For a regular route that runs every thirty minutes or less, a tripper will be required if the maximum load on the regular trip is greater than 125% of the seating capacity. This 125%, known as the load factor , would mean that on a standard low-floor bus with a seating capacity of 38 there would have to be a max load of (38*1.25) = 48 (rounded up) in order to add a tripper. For a regular route that runs more frequently than every thirty minutes, a tripper will be required if the maximum load on the regular trip is greater than 150% of the seating capacity, equivalent to a load of (38*1.5) = 57 on a regular bus. We require a greater load factor for a more frequent route because the consequences of being passed-up are not as great - it is not as big a deal to wait another 10 minutes for a bus as it would be to wait another 30 or 60 minutes. In addition, if a wheelchair user is passed-up at a bus stop federal ADA regulations generally require that the wheelchair be picked up within 30 minutes. What this means is that on a route where the next bus will not arrive for at least thirty minutes, the transit agency must send a special vehicle to pick up the passenger. School trippers are generally not required on routes that run every eight minutes or more because the existing service is enough to absorb the demand within a reasonable time period.
Sometimes the number of students will be so great that more than one tripper will be required. If the students come out in waves to an extent that more than one regular trip could be expected to carry students, then repeat the steps in the above paragraph with following trips. If the students arrive all at once, then count the number of students and divide by 1.5 - that is the total number of trips needed at that period, including regular trips.
At this point you may object that the students do not all have to travel home at the same time - they could wait for a later bus (perhaps passing the time by completing their homework). While making people wait for an empty bus may work for adults (although it is terrible customer service), most schools do not want large numbers of unsupervised and idle students hanging around after school due to the safety and security risks that such a situation presents. The bigger the crowd of students and the longer the delay, the greater the likelihood that a fight will break out.
How Do We Schedule a Tripper?
Trippers should be scheduled to arrive at the school about fifteen minutes before school starts for the day and to leave the school about fifteen minutes after school ends for the day. In addition, trippers should be scheduled to operate before the regular trips. Doing this ensures that any overcrowding (and associated late running) happens on the tripper, as since the tripper (by definition) is likely only operating one trip it does not matter in terms of subsequent on-time performance the tripper arrives at the terminus portion late. In addition, scheduling the tripper before the regular trip allows for passengers to transfer from a tripper to a regular trip in the event that the tripper does not operate the full route (described more below).
When scheduling a tripper, remember that you do not necessarily have to schedule the tripper to operate the whole trip. Passenger loads of the regular trip should be closely analyzed so that the tripper only operates as far as necessary to ensure the other trip is not overcrowded. Practically, this means that after school trippers should begin service at the school, while morning trippers should end service at the school. Morning trippers should begin and after school trippers should end at the closest timepoint before (morning) and after (afternoon) where the bus is no longer necessary for crowd control.