3. Save as provided in article 4 below, no person shall cause or permit any vehicle–
(a)having entered the main eastbound carriageway of the trunk road from the Excelsior Slip Road to proceed in any direction other than eastwards,
(b)proceeding in the offside lane of the Excelsior Slip Road to turn left at the junction with Sipson Road,
(c)proceeding in the main eastbound or westbound carriageway of the trunk road to make a U-turn at the junction with Sipson Road so as to proceed in the opposite direction, or
(d)proceeding in the offside lane of the main eastbound or westbound carriageway of the trunk road at the junction with Sipson Road to turn left or proceed straight ahead.