N24 traffic data : Latest projections

The NRA traffic projections that determine which type of road is required for a particular place are based on an index which had 1995 as its start date. Basically, for every one hundred vehicles in 1995, it was projected that there would be 130 in 2000, 154 in 2003, and so on until the year 2035, when the figure would level out at 230 vehicles.
If you wish to find out how many vehicles there will be on a road in 2020, all you need to know is how many there were in 1995, and multiply that figure by 2.1. This model works quite well for an average road, but is the N24 average?
To begin to answer this question, we looked at the data that has been collected by the NRA Automatic Traffic Counter located near Rathkeevin on the main Cahir to Clonmel road. This counter registers each vehicle passing in each direction on the road, and this data is then accessible from NRA website. Data collection began in 2000, and has been ongoing since (with occasional days of missing data). We know that this counter is very precise as our group did a twelve hour traffic count alongside it, and the figures that we found and the machine found were an exact match.
The way we analysed the figures was to first of all do the projection exactly as the NRA would do with the year 2000 data. The result of this projection is shown in column 3 of the table, where for instance, the projection is for 12406 vehicles in 2020. (This is almost exactly the same as the 12403 vehicles cited in the Traffic & Road Type Report published by Halcrow Barry for the NRA in April 2002).
We then compared the actual traffic figures for 2001, 2002 and 2003 (column 4 of the table) with the projections. As you can see, the actual figures lagged behind the NRA projections. This is important as it shows that traffic on this part of the N24 is not growing at the same pace as traffic in other parts of the country.
To allow for this lower pace of growth, we then made a new set of projections based on the 2003 traffic data. These are shown on red in column 4 below. The interesting thing about these is that they show that by 2035, there will be almost 1000 vehicles less using the road each day than originally predicted.

The implications of this observation are important.
Firstly, economic growth of the order experienced in Ireland was not envisioned when the projections were made. Given that the traffic projections were too high despite a stronger than expected economy indicates that even if economic growth continues at higher than expected rates, the original traffic projections for this segment of the N24 are too high.
Secondly, the projection of the most recent (2003) traffic figures indicates that a dual carriageway would not be justified according to the current recommendations of the NRA’s Design Manual for Roads and Bridges. Even the most basic dual carriageway has a capacity of 26,500 vehicles per day, while a wide single carriageway has a capacity of 13,800 per day. Indeed a standard single carriageway with 2.5metre hard-shoulders has a capacity of 11,600, which is not much different to the projection for 2020 based on the 2003 figures.
Thirdly, if the slower than expected growth rate in traffic volumes continues, then even the projections based on the 2003 data (in red above) will be too high. Whether this is the case will become apparent as the data for 2004 and beyond becomes available.