SEPTA plans to spend up to $154 million for 18 new Regional Rail locomotives, the authority's biggest railroad acquisition in a decade.

The electric locomotives would replace eight aging engines operating on the Lansdale-Doylestown, Paoli-Thorndale, Trenton, and Wilmington-Newark lines, and add capacity to other regional lines.

The SEPTA board is expected to approve the purchase on Thursday, with the locomotives to be delivered in 2018.

SEPTA is buying 13 "Cities Sprinter" ACS-64 locomotives to be built by Siemens Industry Inc., the German conglomerate, at its factory in Sacramento, Calif. The price includes an option for five additional locomotives.

The ACS-64 is the same locomotive Amtrak is buying for use on the Northeast Corridor. One of the first new Amtrak locomotives, which was put into service in early 2014, was involved in the deadly derailment on May 12 at Frankford Junction in Port Richmond. The train wreck killed eight people and injured 200 passengers.

The new SEPTA locomotives are part of the transit authority's increased spending on new vehicles and major construction enabled by a boost in state transportation funding in 2013.

SEPTA plans to spend $535 million in the fiscal year that starts July 1 to buy new vehicles, replace and repair rail bridges, upgrade train stations, and begin overhauling its Center City subway concourse.

In addition to the new locomotives, SEPTA will buy 525 hybrid buses over five years. And it will soon begin the process of procuring 45 bi-level railcars to increase capacity on the Regional Rail lines.

The new locomotives are an adaptation of Siemens' Eurosprinter locomotive, adapted to fit the needs of the North American passenger rail market for speeds up to 125 miles per hour.

The locomotives are the biggest rail purchase by SEPTA since the authority bought 120 new Silverliner V railcars for $274 million in 2006.

The first of those cars was delivered in 2010, the last one in 2013.