When TriMet opened the first segment of its Westside MAX line in August 1997, it also introduced its 200-series Siemens SD600 low-floor cars, the first such transit rolling stock in North America. To do so, it had to modify its existing platforms for the new equipment stock. The platforms were raised a few inches to match the floor height.

At the same time, TriMet also removed the hydraulic lifts at its existing platforms that allowed wheelchair-bound riders to enter and exit the agency's 100-series high-floor cars. Since the new operating pattern matched two 200-series cars or mixed a 200-series and a 100-series, wheelchair users rode on the low-floor cars. They had bridge plates on two side doors that allowed wheelchairs or families with strollers to roll right on and off the cars. By eliminating the lifts, TriMet was able to reduce platform dwell time.

Since then, the agency has purchased all low-floor stock. Its roster includes 52 SD600s (201-252) and 27 SD660s (301-327). It has recently begun deliveries of its latest rolling stock, the Siemens S70, numbered in the 400s. Cars 401-405 are currently on the property and have entered testing prior to entering service later this year, and 17 more are on order.