Many fac­tors de­ter­mine how long it takes to stop a train,

Load plays role in dis­tance a brak­ing freight would travel.

Austin American-Statesman - - FRONT PAGE - By Ben Wear bwear@states­

Trains stop in their own time.

Ev­ery freight train, ev­ery sit­u­a­tion, ev­ery load is dif­fer­ent. The dis­tance it takes to halt a train in an emer­gency is based on mul­ti­ple fac­tors: its speed when the brakes are ap­plied, the track’s in­cline, the num­ber of cars hooked be­hind the lo­co­mo­tives and the load­ing of those cars, the “brake de­lay” in­her­ent in the train’s hy­draulic sys­tem, the fric­tion-caus­ing met­al­lurgy of the wheels and tracks, the weather.

Even the en­gi­neer be­hind the con­trols can’t know on any given day how long it would take to stop the train.

“There is no spe­cific rule of thumb on that,” said Greg Udolph, gen­eral man­ager of the Texas State Rail­road, a freight and tourist line in East Texas run­ning from Pales­tine to Rusk. “If the track is wet with dew, it changes. Every­thing that can af­fect it does. A train takes as long to stop as it takes to stop. Some­times it can be a mile. Some­times it’s less, some­time’s it’s more.”

So even when a con­duc­tor sees some­one far down the track, the train may not be able to stop in time. Fed­eral guide­lines tell com­mer­cial driv­ers to im­me­di­ately evac­u­ate a ve­hi­cle that gets stuck on the tracks.

The public doesn’t yet know at what point the CSX Trans­porta­tion train en­gi­neer per­ceived Tues­day af­ter­noon that the bus stopped up ahead on the tracks in Biloxi, Miss., was not go­ing to move, and de­cided to hit the emer­gency brake. The train was go­ing 26 miles per hour when the en­gi­neer ap­plied the brakes, in­ves­ti­ga­tors with the Na­tional Trans­porta­tion Safety Board said Thurs­day at a Biloxi brief­ing. And the freight, run­ning on a long straight­away through the coastal town, had slowed only to 19 mph when it hit the Echo Trans­porta­tion tour bus high-cen­tered on a hump-shaped cross­ing.

The train and crum­pled bus came to a stop 203 feet down the track, of­fi­cials said. Four Texas tourists died, and 35 oth­ers were hos­pi­tal­ized with in­juries.

The train set was of medium size as freights go, with three lo­co­mo­tives and 52 cars. In­for­ma­tion on the de­gree to which the cars were loaded has not been re­leased. The stop­ping dis­tance would vary widely, Udolph said, de­pend­ing on that load­ing per­cent­age.

Train brakes are ac­ti­vated by air pres­sure, he said. Each car in the line has a pipe run­ning along its un­der­car­riage, and those pipes are con­nected by hoses where the cars meet. Then, be­fore the train de­parts, that pipe sys­tem is pres­sured to 90 psi, said Udolph, who was a train en­gi­neer ear­lier in his ca­reer.

When an en­gi­neer hits the brakes in a nor­mal sit­u­a­tion, some of that air bleeds into the at­tached brake cylin­ders, in turn push­ing brake pads against the wheels through­out the train. The pipe pres­sure might drop only to 80 psi, for in­stance, he said.

“When you put a train into emer­gency, it drops that pres­sure from 90 psi to zero,” Udolph said. “Ba­si­cally, it puts the brakes on as hard as you pos­si­bly can.”

De­pend­ing on the length of the train, there might be a few se­cond de­lay be­tween when the en­gi­neer hits the emer­gency brake and all cylin­ders through­out the train have been pres­sured up.

“Once you put on the emer­gency, you just hang on and wait for it to stop,” Udolph said. “You don’t know. Some en­gi­neers don’t have to do that their en­tire ca­reer.”

He never had to, never had that mo­ment where hu­man lives were at stake in front of his eyes.

“That is the long­est cou­ple of min­utes in an en­gi­neer’s life,” he said. “I know a lot of en­gi­neers who have gone through it. It’s not an easy thing to come back from.”

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