↑ Humble beginnings for freeway phones (July 1998). Western Roads: official journal of Main Roads Western Australia, 21 (2), p.18. Perth: Main Roads Western Australia, 1998.
↑ Country Roads Board Victoria, Sixty-Third Annual Report: for the year ended 30th June, 1976, Burwood, Victoria: Brown, Prior, Anderson, 1976
↑ Downey, David (Mar 13, 2019). "Riverside County to remove 225 highway call boxes, some are never used". The Press-Enterprise. สืบค้นเมื่อ 2019-10-24. In Los Angeles County, for example, more than 1 million calls for aid were placed from call boxes in 1988, when the L.A.-area had 4,500 highway phones, Jager said. Fast forward to today and the number of call boxes stands at 576.
