An Assembly member whose brother and sister-in-law were killed by a drunk driver wants legislation for a speed limit of 20mph to be introduced for residential areas.
But the SDLP's Pat Ramsey has been warned the new, lower limit would take up to £24m out of the public purse in road signage costs alone.
The Foyle MLA's campaign comes almost 20 years after he lost his brother Ray and sister-in-law Michelle in a horrific crash in Co Donegal which left their two young children injured.
Pat, the girls' uncle, insists the five-year term imposed on the driver was not enough – and is now launching a Private Member's Bill to reduce the speed limit.
He plans to meet Regional Development Minister Danny Kennedy and Environment Minister Mark H Durkan and will give evidence to the Assembly's environment committee today.
He said: "A pedestrian hit by a vehicle travelling at 20mph has a 2.5% or one-in-40 chance of being killed or a 97.5% chance of surviving.
"That is in stark contrast to a pedestrian hit by a car travelling at 30mph, who has a 20% or one-in-five chance of being killed and an 80% chance of survival." The 20mph limit, he says, should include schools and school entrances, school playing fields, residential roads, play parks, unclassified roads and city centres.
DUP chairman of the committee, Jimmy Spratt, responded: "We are talking about 4,600 kilometres of roadway here. If my mathematics are right, that would cost somewhere in the region of £23m or £24m for signage alone, The bottom line is that in law we cannot enforce a speed limit unless there is signage."
Sinn Fein's Declan McAleer argued: "Unfortunately, there have been a number of fatalities in my constituency so far this year. The implementation of 20mph zones would not have prevented any of those deaths."