EVERETT — Community Transit is preparing to buy 17 more double-decker buses, adding to its existing fleet of 45 “Double Talls.”

The agency’s board of directors authorized the purchase Thursday. The buses from manufacturer Alexander Dennis are expected to arrive in mid- to late 2017.

Community Transit leased its first double-decker bus in 2007. Community Transit put 23 “Double Talls” in service in 2011 and added 22 more last year at a cost of about $900,000 each.

The tall buses seat about 80 people each and are used on commuter routes.

Sound Transit also is building up its double-decker fleet, announcing plans last month to order 32 more on top of the five in its fleet. Sound Transit contracts with Community Transit to operate its double-deckers.