Sir, - Having just read your interesting series of articles on gridlock in Dublin, two main contributing factors which were omitted come to mind.Firstly: the differences in travelling times for by motorists coming into the city from the suburbs when the schools are open and when they are on holidays. Perhaps some variation of school opening times should be considered.Secondly, as someone who does a lot of city driving between 10 a.m. and 2 p.m. each day, I find the lack of awareness of other road users extremely frustrating. During rush-hour traffic, everyone is in two lanes and moving as quickly as possible. Off-peak, you are likely to find a car stradding the lanes or a car trying to turn right also blocking two lanes.This lack of lane awareness is a far greater contributor to road rage than mere heavy traffic. - Yours, etc.,Fergus Madden,Taney Avenue,Dublin 14.