The CBS is a Transition era layout. We run mostly 40 ft cars, 4 axle diesel and Small steam. Only because this looks much better around 072 and 081 curves. Also gives the layout a much larger appearance. My kids do like the modern era of course. So I have plenty of larger 6 axle modern motive and 50 ft cars. Not too many cars larger than that, as again they don't look that good on my tight curves. However, we have never had a problem, kadee to kadee, doing anything.