The Milwaukee County Zoo is replacing the zoo train's steam locomotive engines

The Milwaukee County Zoo's popular zoo train will undergo some changes this year.

The train's two steam locomotive engines will leave the zoo; they've been sold to the Riverside & Great Northern Preservation Society in Wisconsin Dells. The No. 1916 engine is leaving the zoo April 1, and the No. 1924 engine will leave Oct. 31.

The train will continue to use its two diesel engines and is buying two custom-built diesel engines to replace the steam engines.

According to the zoo's announcement and a frequently-asked-questions page compiled by the zoo, the steam engines are being retired because the zoo "has had a significant concern with operating the steam locomotives while still following its mission of conservation and sustainability."

The zoo anticipates the first new diesel engine — expected to arrive later this year or early in 2025 — will reduce particulate emissions by 90%.

The passenger coaches won't be affected by the change to the engines, although preventive maintenance is performed on the coaches each year. The new engines are expected to allow the zoo train to run year-round, weather permitting. Currently, the zoo train only operates April through November.

The steam engines will be preserved and continue to operate in their new home; Riverside & Great Northern Preservation Society functions as a living museum. The zoo is planning to announce one more chance for train riders to experience the No. 1924 steam engine in a limited run before its Oct. 31 departure.

The train has been at the Milwaukee County Zoo since 1958, and the steam engines were gifts from The Milwaukee Journal; they're named after then-Journal executives Harry Grant and Irwin Maier.

This article originally appeared on Milwaukee Journal Sentinel: The Milwaukee County Zoo train's steam locomotives are being retired