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Perhaps a look into the PRIIA 305 specification and preceeding recommendations sheds some light of his brake assumptions. From Specification Recommendations For Procurement of Passenger Locomotives 2010: <a href="http://www.highspeed-rail.org/Documents/PRIIA%20305%20DocSpec%20and%20other%20NGEC%20Documents/Locomotive%20PRIIA%20305%20Spec%202010%20Draft%20Rev2.doc">http://www.highspeed-rail.org/Documents/PRIIA%20305%20DocSpec%20and%20other%20NGEC%20Documents/Locomotive%20PRIIA%20305%20Spec%202010%20Draft%20Rev2.doc</a>  <h3><a name="_Toc267895776"></a>1.1.1                    Performance Criteria</h3> ·         Full-service, air-only braking shall not be less than 1.3 MPHPS ·         Emergency, air-only braking shall not be less than 1.6 MPHPS ·         Full-service, blended braking shall not be less than 1.6 MPHPS ·         Emergency, blended braking shall not be less than 2.0 MPHPS ·         Air-only brake shall be used below 5 mph, and immediate motoring shall be available to engineman between 0-5 mph ·         Blended brake shall be available when throttle is in idle ·         Pneumatic priority shall be given in emergency and dynamic priority on service-rate applications, pneumatic brake shall be fail safe against loss of dynamic brake ·         Wheel slide detection/correction shall be in conjunction with dynamic and pneumatic brake during blending ·         Brake Cylinder Pressure (B.C.P.) shall be limited to emergency maximum when independent brake valve is applied during blending Final specification is different: <a href="http://www.idot.illinois.gov/Assets/uploads/files/Doing-Business/RFP/Multi-State-locomotive/PRIIA%20Locomotive%20Spec%20305-005%20Rev%20A%20-%202012jul10.pdf">http://www.idot.illinois.gov/Assets/uploads/files/Doing-Business/RFP/Multi-State-locomotive/PRIIA%20Locomotive%20Spec%20305-005%20Rev%20A%20-%202012jul10.pdf</a> On page 104 are the performance criteria. Sorry no copy and paste possible. So in short: Full-service, air only for a single locomotive from 125 mph, the stopping distance shall be no more than 9,000 ft Emergency, air only for a single locomotive from 125 mph, the stopping distance shall be no more than 8,000 ft There is no large margin between full-service and air-only required. And according to the preceeding recommendations, air-only emergency and blended full service would have provided the same decelleration of 1.6 mph/sec What ever it is worth. Regards, Volker Edit: I tried to reactive my physics knowledge: Stopping distance of 9,000 ft from 125 mph needs a deceleration of 1.27 mph/sec; stopping distance of 8,000 ft from 125 mph needs 1.43 mph/sec deceleration.
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