The passenger locomotives are being stressed by the high speeds and high daily mileage. Freight locomotives are not stressed like passenger locomotives
They are stressed differently. Just for the slip problems discussed elsewhere, they need sand re-supply, and wheel re-profiling if there are blocked wheels. Add to that the consequences of using axle-hung motors (f.e. the bogie frame damage, hit even the TRAXX 2).
passenger locomotives become obsolete more quickly
Do they? Express locos over the past century yes, due to the continually increasing maximum speeds; but old locos (ÖBB 1042, MÁV MÁV V43.10, DB 110, 111, SNCF 8500), some with with retrofitting (ÖBB, ÖBB 1142 and 1144, MÁV V43.20 and .30) survive just fine in local service. *Lunatic*, n. One whose delusions are out of fashion.
The Austrian 1042/1142 locomotives served a long life, but the future for the 1044/1144 series has gotten a lot more uncertain, and the 1014/1114 series are about finished. The rapidly expanding demand for both passenger and freight service meant that it was hard to acquire locomotives fast enough, but it is no longer uncommon to see a Taurus lok on a stopping service now. The DB class 110 only have survived as long as they have because of the inadequacy of the former DR Class 143 loks with their 120kph top speed. In spite of the vast numbers of this model I would be surprised to see many survive to 2020, except for the few being converted to Class 114.
If the TRAXX2 are suffering bogie damage from their Tatzlager traction motors then they must have been designed by the same person who designed the axles for the DB Class 403, 411, 415, and 481 units.
