Questions on ...speed limiters&deployment of bendies

bus911 SG

1a.How do the speed limiters work?Controlling engine?Controlling by speedometers(i.e when speedometer reads as 60, then speedlimiters start their work)E.g SBS926E which I caught speeding at 80-85km/h--this bus speedometer does not work-reads 0km/h when travelling
b.What happens when speed is at 60km/h and driver press accelerator harder..nothing happens or engine increase but speed remains?
c.If bus is at 60km/h on a flat road then there is a slope, will the bus speed increase?
d.Are all speed limiters working/speed-proof(even when not tempted)?Can they be tempted with?

2.Why are bendies deployed at the wrong time for service911?
a.Why are there no bendies deployed on weekdays(only sometimes have) when there is the demand?But on weekends there are many(especially on Sundays)-even after midnight when the demand is very low.

leeJZ SG

I think the speedos work by cutting off fuel supply to the engine when it reaches 60 kph.

^tamago^ SG

1a. according to mannesmann vdo, supplier of all our public bus speed limiters in singapore:
"With the Pedal Interface I, it is possible to control the pedal input signal before it reaches the engine ECU (electronic controller unit) so that a predefined speed is never exceeded."

thus, it is likely the faulty speedometer leads to the ECU not knowing the speed of the vehicle at the moment thus the speed limiter does not kick in at all. however, a faulty component of the ECU is serious as it may complicate things such as temperature control of the engine etc.

note also that a "variable" version of the speed limiter is also available for better & more flexible speed control.

1b. engine runs but speed remains. however, rpm & gear change will stay at that of 60kph thus the pitch of the engine remains the same.

1c. from my observations, buses will remain at 60kph, though i dunno how this is accomplished since it is stated that the speed limiter acts on the pedal input signal. and while most is locked at about 60kph (see below why i said "about" ), there are a few exceptions around.

1d. according to tibs (now SMRT Bus), the directive given to bus drivers is to report a defective speed limiter only if they have found their vehicles to have exceeded 70kph. and there are cases that buses' speed is limited at 6X kph even though the set speed of the speed limiter is 60kph, though that is deemed "normal" to the bus companies and probably LTA too. thus it is about 60kph.

if u tempt with the speed limiter, of course its top speed will change. if the speed limiter is working of course it will be speed-proof (unless there is a manufacturer's defect, which should be informed by the bus driver to their respective supervisors).