Traffic is crawling on a highway and a transit bus sweeps past you along the paved shoulder. You then notice a sign reading "DO NOT DRIVE ON PAVED SHOULDER — AUTHORIZED BUSES EXCEPTED". Was the bus breaking the law?

Correct answer: D. No — this section has a designated bus by-pass shoulder, which authorized buses may use and other traffic may not

No. Some highway sections have a legally designated "bus by-pass shoulder", where the paved shoulder may be used by authorized buses and by nobody else. Book 5 explains that the purpose of these signs "is to identify parts of highways that are designated as having paved shoulders for use by authorized buses and to indicate to general traffic that use of the shoulder is prohibited." An AUTHORIZED BUSES USING SHOULDER BEGINS sign marks the start of such a section and an ENDS sign closes it, with the DO NOT DRIVE ON PAVED SHOULDER sign repeated in between. Book 5 also notes that "bus by-pass shoulders are not the same as reserved lanes" — the shoulder is not a lane you may join when the bus has gone.

Source: MTO Driver's Handbook: Ontario Traffic Manual, Book 5 — Regulatory Signs (December 2021), Section 15.4 — Bus By-Pass Shoulder signs (Rb-98, Rb-99, Rb-100)