Irish rail fleet and infrastructure plans

You notice the diesel fumes in Connolly more than heuston for some reason. Limerick traps the fumes too?

You can see the blue haze in the air in Connolly on summer days. A lot of things on Irish Rail seem to be considered acceptable - crush overcrowding isn't considered dangerous for instance - until someone dies I guess

Gen van shouldn't be a big issue, as it's outside the canopy.

no.

tunnels would prohibit it, then you would have to rebuild bridges (doable but no real point)

what might be doable is to extend platforms on the dublin suburban to allow 12 car trains but we are way away from that if it even can be done, it will certainly cost.

the most important thing now is to insure all trains are at the capacity they need at all times.

Almost definitely no. In theory everything is possible but there is a long list of problems with it that will realistically prevent it from ever happening here. The most significant problem is our loading gauge (not to be confused with track gauge) which is quite restrictive. This includes many things such as axle load, maximum train width, and most problematic maximum train height. Many bridges, tunnels, and other structures on the network are quite old and are either just tall enough to allow for OHLEs or have to be rebuilt/raised. This has already become a difficult and expensive problem just to get height enough for a single deck fleet (such as for electrification to Maynooth). Trying to then further add enough clearance for DD trains would be insanely difficult and expensive, as I doubt even much of the new infrastructure was designed to support it.

There are also potentially problems with our OHLE height and platform height. Raising OHLE isn't necessarily a difficult task (at least not compared to many other infrastructure upgrades) but it would be somewhat disruptive and may require modifications to the rolling stock. I don't know much about OHLE heights or what changes would be required as the information can be hard to find, but considering the visual height difference in pictures and that DD sets would already be 30-40cm higher than anything we currently operate it is a consideration. As for the platform height, ours are just quite high compared to many other places (or at least mainland europe) and I am not aware of anywhere that operates DDs with such a high platform height. I am not sure if this would actually be a problem, in fact in many ways it being high is good, as it makes level boarding rolling stock much easier to design. But again, it is just another way our network is different and could affect the feasibility of DD rolling stock.

However, even if it is possible to replace all the bridges, tunnels, etc that are too low, the amount of work it would take would be much better spent on just about anything else. There is still a number of improvements and upgrades would massively increase capacity that should be done before even considering DD trains. The most important of which are:

• Ensuring all services run as full length: Many services including that 4-car one you were on are causing a lot of capacity issues on our network. It would go a long way if all services are extending to 164m 8-cars services for commuter sets, 164m 10-cars services for the new DART. This currently isn't possible as there simply aren't enough trains in the fleet for everything to operate at full length, but from next year new DART units will enter service and this should allow almost if not all commuter services to operate at full length.
• Increasing frequency: This is probably the most important as currently our frequency isn't very good by international standards. DART+ should allow most lines to operate at 5-minute frequency or 12 trains per hour, although that will be shared by DARTs, outer commuters (such as those to Dundalk), and IC services. However, with the right upgrades it would be possible to exceed to 20 tph and possibly even approach 30tph such as on Paris's RER A. Now these upgrades would cost billions, but so would everything required to allow DD trains, and the frequency improvements are the long-term upgrade Dublin really needs.

If the above still isn't enough there are other options to consider as well such as extending the platforms of our stations or building metro lines to relieve pressure on the DART line (such as along Malahide Rd or the N11). The former is anywhere from easy to very difficult depending on the station. Also, while 164m is not short for a commuter service by any means, some commuter networks do use >200m trains, and generally longer trains would reduce dwell times compared to DDs as you would have more doors per passenger. A new metro line on the other hand would be a much bigger intervention (not even getting into that we don't have a metro yet, this is just a hypothetical way you can fix overcapacity), but also the primary benefit would be to increase rail catchment. Relieving pressure from the DART would just be the benefit of being more convenient for some users than say connecting to the DART via an orbital bus. And again, while these would be expensive options, they are much better long-term interventions to cover before considering DD trains, as they would have a much greater network benefit on top of just being better value for money.