Don't do a double take when double-decker buses start rolling into Kitchener and Guelph Saturday.

GO is phasing in the 80-seat, two-level buses starting 7:30 a.m. Saturday on routes between Kitchener and the Square One terminal in Mississauga, said Malon Edwards, spokesperson for Metrolinx, which operates GO.

The Ontario government transit agency is in the process of buying 70 of the two-level buses, bringing the total in service to 117 by June. That means double deckers will make up nearly a quarter of the GO bus fleet by then, he said.

"As additional buses arrive over the next few months, we will continue to add double-deck buses to additional trips across the GO network to meet customer demand for extra capacity," he said.

Go first purchased 22 double deck buses in 2008. In April, another 25 were ordered, for service in the Toronto-Hamilton area. Buses coming to Kitchener and Guelph routes are in a third order. They're made by Alexander Dennis Ltd. in Scotland.

Adding tall buses mean some changes to routing, to clear overhead obstructions, GO says.

•At the Kitchener bus terminal, the GO bus stops move onto Charles Street. Westbound buses will stop at the north side of the terminal. Eastbound coaches will stop on the south side of the terminal.

•At the Guelph terminal, GO buses will no longer run along Wyndham Street. They'll use Gordon, Norfolk and Macdonell streets to stop at the Guelph station.

The new buses cost $750,000 each. Single deck buses carry 55 people, and cost $550,000. Two double-deckers can replace three single level highway coaches.

A television monitor on the stairs shows riders if there are empty seats on the upper level. Reading lights and power outlets allow riders to work, read and use electronics.

The buses are equipped with a global position system that sounds an alarm in a GO control room if they stray off their approved routes. The buses can be stopped remotely if they're in danger of hitting a bridge or other obstruction.