Lighting fires on or over a highway, discharging firearm or firework - If a person without lawful authority or reasonable excuse: (a) Lights any fire on or over a highway which consists of or comprises a carriageway, or (b) Discharges any firearm or firework within 50 feet of the centre of such a highway, and in consequence, a user of the highway is injured, interrupted, or endangered, that person is guilty of an offence.