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N52 - Tullamore to Kilbeggan (M6) [route options published]

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Comments



  • I often wonder is AADT a bit of a blunt instrument sometimes. Probably gives a better indication on commuter routes where a high volume of traffic is concentrated in one direction in the morning and the other direction in the evening, meaning the road is overloaded. On a stretch of road like this, the traffic is probably spread more evenly in both directions over the day. Roads with a similar AADT would be the N3 Cavan bypass and N80 Carlow bypass but I don't think anyone would suggest dual carriageway on them. Also, the biggest constraints after upgrade on this road (N52) will likely be the roundabouts at either end, not the number of lanes in between.

    Worth noting that the TII document states for this project; Cross-section: Expressway / TBD. Obviously not yet confirmed. It also states Forecast Cost Range: €80-100m which is based on €10m/km for 2+2 as used elsewhere. Given the route will almost certainly encompass the existing relatively recent good quality sections of N52 at northern and southern end, you are talking about ~3.5km of offline new build 2+2 plus just under 5km of single carriageway upgrade. Around €50m is probably a more accurate cost for 2+2 but even that is ridiculous for a minute or two reduction in journey time and no bottlenecks bypassed. I would see something like the recent N52 Turin to Billistown Realignment as what should happen here. That was 6km of mostly offline new build Type 1 Single Carriageway which cost €12.6m. Something similar between Tullamore and M6 J5 would cost less than €20m. Put the other €30m into an upgrade which bypasses a town and gives a meaningful reduction in journey time, plenty of candidates out there.




  • Pete_Cavan wrote: »
    I often wonder is AADT a bit of a blunt instrument sometimes. Probably gives a better indication on commuter routes where a high volume of traffic is concentrated in one direction in the morning and the other direction in the evening, meaning the road is overloaded. On a stretch of road like this, the traffic is probably spread more evenly in both directions over the day. Roads with a similar AADT would be the N3 Cavan bypass and N80 Carlow bypass but I don't think anyone would suggest dual carriageway on them. Also, the biggest constraints after upgrade on this road (N52) will likely be the roundabouts at either end, not the number of lanes in between.

    Worth noting that the TII document states for this project; Cross-section: Expressway / TBD. Obviously not yet confirmed. It also states Forecast Cost Range: €80-100m which is based on €10m/km for 2+2 as used elsewhere. Given the route will almost certainly encompass the existing relatively recent good quality sections of N52 at northern and southern end, you are talking about ~3.5km of offline new build 2+2 plus just under 5km of single carriageway upgrade. Around €50m is probably a more accurate cost for 2+2 but even that is ridiculous for a minute or two reduction in journey time and no bottlenecks bypassed. I would see something like the recent N52 Turin to Billistown Realignment as what should happen here. That was 6km of mostly offline new build Type 1 Single Carriageway which cost €12.6m. Something similar between Tullamore and M6 J5 would cost less than €20m. Put the other €30m into an upgrade which bypasses a town and gives a meaningful reduction in journey time, plenty of candidates out there.

    AADT is one of the criteria used in the design of road upgrades. And as you say this project hasn’t been fully designed yet. In the old NRA days it was to be 2+2.

    The traffic on this stretch is 3 times higher than the Turin section at 14000. While most of it is commuter traffic it is a little different than ones nearer a city. Traffic out of Tullamore to Dublin starts between 6 and 7 am. Then you have the traffic commuting into Tullamore between 8 and 9. With the opposite from about 5pm to 7 or 8pm. There is also a high number of cross country HGV traffic.

    Journey reduction time isn’t the only consideration for a scheme. Traffic safety, local safety and journey reliability are also things to be taken into account.

    This road needs to be improved at some stage and it makes sense for 2+2 to be at least a strong contender. No one is saying it’s the most critical scheme in the country or even on the N52 but it has its merits.




  • AADT is only one measure, and strictly speaking the 20,000 figure is "Maximum AADT to maintain Level of Service class D or better".

    That second bit, Level of Service (LOS), is a rough measure of how freely traffic can flow, rated from Class A to Class F. Ideally, you want class A (all traffic can drive up to the design speed of the road), but in a world without unlimited money and land, you usually have to settle for lower classes of service. D is the last "flowing" traffic class. E and F (the worst) include dramatic slowdowns and (for F) traffic coming to a complete stop.

    Commuter routes will occasionally see LOS E and F, but never for very long (it just seems like it, but really it's often less than 5-10 minutes), and because LOS is usually an hourly average across the whole day, this is compensated for by the higher road capacity allowing much freer moving traffic at off-peak times.

    Rural roads have a different problem to commuter routes: slow vehicles. Suburban commuters drive up (and beyond) to the permitted speed limit if able to, and only slow down due to the high volume of traffic, but on rural roads, slowdowns are mainly from heavy vehicles that are inherently limited to lower speeds. This creates a different kind of congestion, but it all comes out the same way: a lower Level of Service.


    All that said, yes, some routes are being specified at a higher level of service than they might actually need, but there are more factors than just capacity. Dual carriageways avoid the kind of overtaking fatalities that happen regularly on lightly-trafficked rural roads, and there's plenty of evidence that flipping between single and dual carriageway roads increases the risk of accidents.




  • Emerging preferred route due this summer. Date tbc.




  • marno21 wrote: »
    Emerging preferred route due this summer. Date tbc.

    Spoiler: It'll follow the existing route closely.


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  • Prefered route is announced. Making full use of the upgraded bits of the Tullamore bypass and the stretch from the M6 roundabout. (Combining option 2 and 3)


    https://www.offalyindependent.ie/2021/09/17/a-proposed-route-corridor-for-the-new-tullamore-to-kilbeggan-road-has-been-published/





  • The logical choice. Looks like there will only be one junction along 8km of road between the existing roundabouts at either end plus a parallel R or L road all the way for local traffic.



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