The location of toll plazas is key. If rationing is your goal, toll booths should be located in areas of heavy congestion and priced to deter use, for example at certain times of the day.
At present the choice of locations in Ireland clearly signal a decision to toll for revenue generation.The latest example is in Drogheda on the main Dublin to Belfast route, where two new toll plazas are to be built on the northern entrance and exit sliproads of the M1 at Drogheda and another on the M1 motorway near Gormanston, south of Drogheda town.
Normally toll plazas are located next to the section of road built under the PPP scheme.
However, the consortium awarded the contract for operating the Drogheda tolls will partly finance the completion of the rest of the route to the border, notably the Dundalk to Newry bypass.
Locals have questioned the reasoning behind collecting tolls from drivers this far south from where the PPP funding will actually help build the Dundalk road. The NRA defends the choice of location, saying the winning consortium will also be responsible for the maintenance of the 50km of road from Drogheda to the border.
They also highlight the need to ensure a scheme can stand up financially so they need to locate the toll plazas in areas where there is less chance of avoidance and also where there is a financial incentive to locate.
Locals have also been concerned that anyone coming from Belfast or other points north and calling in to the town will be tolled twice: once on leaving the M1 and again at Gormanstown.
To remedy this, the NRA has come up with a three-hour window, whereby motorists pay one toll within the three-hour time period.
Those coming from the North can pay at the exit off the M1, enter Drogheda and do not have to pay again at the main M1 toll plaza at Gormanstown provided they exit within the allotted time.
For the NRA the main concern was to avoid Drogheda becoming what some have referred to as a "rat run", whereby drivers coming from the North left the motorway at Drogheda so as to dodge the toll plaza further down the M1 at Gormanston.
Similarly for those heading north from Dublin, they could have left the motorway before Gormanstown and rejoined in Drogheda. The problems encountered in Drogheda should provide some lessons for the next phases of tolling in Ireland, most likely the Kinnegad toll plazas, due to open in 2006.