What factors determine the length/number of riders per train?

[I'veGotFourB&MsInMyGarden]

My mum (not an enthusiast) asked me how many people you can have on a rollercoaster. I said it depends on the number of seats per train. My mum replied with why can't you just make the train longer? I couldn't really answer this because at what point would you stop? (Cue my mother suggesting Thorpe Park's Stealth with 10 car/40 rider trains for increased capacity) We came to the conclusion that it's probably something to do with weight and forces maybe?

If anyone has the physics or maths of how manufacturers/parks decide the length and number of riders per train I would appreciate knowing. Thanks guys

 

[MLDesigns]

Interesting, complex question. More cars per train does mean more riders, but it also means that the layout has to be designed "carefully", or in a way that doesn't exert too many forces on the front/end of the train. This will likely result in a less thrilling ride, as the train is less capable of dynamic elements & pacing. Weight and forces surely play a role, but I would say one of the biggest factors is the hourly capacity of the ride that the park desires.

If a park asks for a ride that can do 1000 people/hour, there's probably different combinations (# of trains, # of cars per train) that can achieve that, and it's probably a back & forth process to find that perfect balance. Look at Velocicoaster for example. It's the only one of its kind running 6 cars, cause the park probably required a higher capacity based on their attendance. Theoretically, it could have had 7 or 8 cars to help with capacity, but then the layout would have to have been designed very differently to account for that.

Curious if anyone else has a take on this!

 

[HandsUpPantsDown]

Station size is one limitation, perhaps a park cannot fit a long train.
The layout has to work with the train length, if a coaster has a long train but very tight hills and/or elements close together, the front of the train may already be finished with element 1 and into element 2 before the back of the train is even at the bottom of the first drop, means theres a weird push-pull force on the train like an accordian which can stress the hitch connection between cars. Ideally the majority of the length train should be experiencing similar forces at all times. This is also why eurofighters have 2 rows and a compact footprint

 

[Matt N]

As @MLDesigns has already said, I imagine it comes down to the throughput requirements the park specifies.

However, I’d also imagine that it might be influenced in part by budget, as longer trains require a more drawn out layout to produce the same level of force. Force = Mass * Acceleration, so as a longer train will contain more mass, the corners and such need to be more drawn out to prevent whiplash or excessive g-forces. This requires more track, so increases the budget required to build the ride.

In the aforementioned case study of VelociCoaster, Universal had the budget to build a ride with drawn-out enough profiling for 24-rider trains. In the case of a different Intamin LSM Launch Coaster example, Gotham City Escape, Parque Warner likely didn’t have the budget for the big, drawn out elements of a ride like VelociCoaster, so that ride has tighter, smaller elements and smaller trains.

 

[Eyebrows]

Force = Mass * Acceleration, so as a longer train will contain more mass, the corners and such need to be more drawn out to prevent whiplash or excessive g-forces.

This… isn’t quite how it works. What we call “G-force” is actually a measure of acceleration, not force. One G is equivalent to the downward acceleration we feel due to the Earth’s gravity, or 9.8 m/s^2. On tight turns and valleys, the radial acceleration produced by the curve in the train’s path exceeds 1G, and we feel heavier than we ordinarily do because the downward acceleration we are experiencing is over 1G.

 

[RevolutionRuleZ]

Anyone who rode the 3 big wooden coasters at BPB in the 90s may remember the days of 4 car trains.

Imagine all the tears we would had today if the back row was a car further back!

 

[Sticky_T_Wicky]

MLD nailed it.

I recall seeing an Alan Schilke interview (linked below) around the time of opening of Steel Vengeance and when discussing the 90 degree drop, his comment was “that happens right at 200 feet for this length of train”.

B&M Dive’s against B&M Giga’s are another example of train length mattering with regards to sharpness/suddenness. Fury has a 320-foot drop but only gets to 81 degrees due to its longer train (and not slowing down much if at all at the top of the lift) whereas a coaster like Valravn gets to 90 degrees with only a 214-foot drop and now there is Dr. Diabolical which gets to 95 degrees on only a 150-foot drop. I also presume the new dive coaster at Dorney will probably get to something like 96 degrees with its 167-foot height.

To expand on how parks/manufacturers design coasters, it is a balancing act of having a thrilling yet comfortable coaster while meeting some sort of capacity requirement. Using SteVe again, it has a published capacity (per RCDB) of 1,200 rider per hour meaning 50 dispatches per hour with its 24 riders per train. Had the train been able to hold 28 riders with 50 dispatches an hour, it could have done theoretically 1,400 riders per hour but the first drop would not have gotten to 90 degrees and other elements of the ride would not have been as sharp/sudden… ironically enough it probably would’ve shortened the track length and potentially the ride time marginally due to not having as sharp/sudden elements. Edit (I didn't finish my thought): And the ironic part is that with the shorter ride time, it potentially could've boosted capacity even more.

 

[Hyde]

As everyone is affirming; it's experienced forces that dictate train length, and want for mitigating high g-force for back-of-train riders. A good example is Voyage at Holiday World, which initially operated with a 7-car train that was later revised to 6 cars (after the failure of trying out Gravity Group's Timberliner trains) - a move rationalized to reduce ride forces both for the rider and coaster structure.

 

[Eyebrows]

a move rationalized to reduce ride forces both for the rider and coaster structure.

Don’t forget that two 6-car trains must cost a lot less than three 7-car trains!

 

[Hyde]

Don’t forget that two 6-car trains must cost a lot less than three 7-car trains!

It's less the capital cost of the trains, moreso the parts and labor of upkeep of Voyage track. Holiday World continues at a pace of replacing a solid 10-20% of track annually (this year was focused on the outbound airtime hills) - so anything to reduce stress on the track is a welcome cost saver!

For the trains themselves, PTC actually offers standard winter maintenance service (https://www.philadelphiatoboggancoastersinc.com/services/roller-coaster-car-winter-maintenance/), which is neat support for a long-chronicled company!