A green arrow pointing down means the lane is open and you can proceed in that lane.
Go (lane open)
A red X means the lane is closed. You must stop. You must not pass this sign. It has the same effect as a stop sign.
Stop (lane closed)
A green arrow pointing to the left means you must move into the left-hand lane. In doing so you must observe the general rules of the road about safely changing lanes.
Move into the left-hand lane
A green arrow pointing to the right means you must move into the right-hand lane. In doing so you must observe the general rules of the road relating to safely changing lanes.
Move into the right-hand lane
Where a driver proceeds beyond one of the above traffic lane control signs other than in accordance with the sign or without yielding, they will be liable for a fixed charge of €60.