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Longitudinal Train Dynamics 269
taken on the vehicle floor) is quoted below.
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
N MV ¼ 6 ð a XP95Þ 2 þða YP95Þ 2 þða ZP95Þ 2
q
ð 9 : 23Þ
where a XP is acceleration in the longitudinal direction; a YP is acceleration inthe lateral direction;
and a ZP is acceleration in the vertical direction.
Afurther equation isavailable for standing passengers, this time using 50 percentile points
from event distributions.
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N VD ¼ 3 16ð a XP50Þ 2 þ 4 ð a YP50 Þ 2 þða ZP50Þ 2 þ 5 ð a ZP95Þ 2
q
ð 9 : 24Þ
Ride criteria using the above index parameters is: N , 1: very comfortable; 1 , N , 2:
comfortable; 2 , N , 4: medium; 4 , N , 5: uncomfortable; and N . 5: very uncomfortable.
VI. TRAIN MANAGEMENT AND DRIVING PRACTICES
A . T RAIN M ANAGEMENT AND D RIVING P RACTICES
Train management and driving practices has received considerable attention in literature dating
back several decades. Technology developments, such as the transitions from steam to dieselelectric
locomotives, improved locomotive traction control systems, remote control locomotives,
operation ofvery long heavy haul units trains, and the operation of high speed passenger services,
have ensured that this area continues to evolve. Train management and driving practices will differ
for different rail operations. Suburban train drivers will be motivated primarily by the need to run on
time. Asecondary consideration may be energy consumption. Longitudinal dynamics will have
minimal consideration as cars are connected with minimal slack and usually have distributed
traction and slip controls for both traction and braking. Passenger express services will be similarly
motivated. Slow passenger services with locomotive hauled passenger cars will share the concerns
of running ontime with the next priority being the smoothness of passenger ride. Passenger train
driver practice often includes energy consumptive power braking tominimise slack action. Where
locomotives have excess power, train drivers have been known tooperate with aminimum brake
application on for several kilometres to reduce slack action over undulations. Mixed freight train
practice, while not motivated by passenger comfort, will share some similar driving practices to
ensure train stability. This is particularly the case when trains are operated with mixes of empty and
loaded wagons. Running on time will be an emphasis on some systems depending on the type of
freight. Differing from passenger systems, energy consumption is asignificant freight cost factor
and is emphasised in freight operations. The operation of bulk product/uniform module type freight
trains (unit trains or blocktrains), e.g., carrying minerals, grain, containers etc, can be optimised to
the specific source/destination requirements. In some cases, timeliness is asecondary concern while
tonnage per week targets must beachieved.
Despite the differences inoperation, acommon thread to train management is the issue of
speed control and hence management of train momentum. For suburban passenger trains, speed
must be managed to ensure timeliness and adequate stopping distances for signals and for
positioning at platforms. For longer locomotive hauled passenger, freight, and heavy haul unit
trains, the problem of momentum control becomes even more significant due to the larger masses
involved. Ingeneral, itisdesirable to apply power asgradually as possible until in-train slack is
taken up. During running it is desirable to minimise braking and energy wastage utilising coasting
where possible. Route running schedules will limit the amount of time that the train can coast.
Longer trains can coast over undulating track more easily than shorter trains due to grade forces
being partially balanced within the train length. Stopping is achieved at several different rates.
© 2006 by Taylor & Francis Group, LLC