The interchange of the Allen and Highway 401 is a hybrid of the "turbine" and "clover-stack". The Allen proceeds on bridges over the lanes of the 401, with ramps from the Allen to 401 passing overhead. The interchange also serves to connect Yorkdale Road with the 401. The exit from the northbound Allen to the 401 serves as a ramp to both directions of the 401, with two lanes proceeding north of the 401. Similarly, two lanes are provided southbound over the 401, and access from the eastbound and westbound 401 merges with the Allen south of Yorkdale Road. Access to Yorkdale Road from the eastbound 401 is provided at the partial Dufferin Street interchange to the west. The southbound ramp from the Allen to the eastbound 401 flies over the whole interchange and connects with the eastbound 401 collector lanes. The interchange is one of the few on Highway 401 that uses conventional light poles instead of high-mast lighting due to the nearby Downsview Airport. The subway is situated on bridges over the 401 between the northbound and southbound lanes.