Infrastructure – design big and design long

Creating resilient infrastructure means responding to change now but crucially designing in solutions for changes in the future, says David Waboso.

Infrastructure is fundamentally important to our modern way of life. Though often taken for granted, it has a huge impact when it's not there. How we make infrastructure investment decisions, over what length of time, and how we grow and sustain our national and international capability to design, build, operate and maintain it, are themes I hope to return to.

The weather, a national obsession (and rightly so in recent years), is relevant to this, following this year's floods, last winter's long cold spell and in between, some lovely hot summer days. I'll cover some aspects of how the Tube's design, upgrade, operation and maintenance has coped with wet, cold and hot weather.

Cooling the Underground

Let's start with the heat. When I came to the Underground in 2005 as Director of Engineering, one of my first challenges was how to get a grip on rising temperatures ahead of the planned significant increases in train timetables in hot deep tube tunnels. We assembled a team of some of the brightest engineers in the field, added a sprinkling of project management and looked at priorities – which lines and stations were already busy and warm and were about to get their upgrades.

One of the early lines we looked at was the Victoria line which was entirely underground (most of the Tube is part surface and part underground but the Vic is all underground) and already quite warm in the summer months. It was also about to receive an upgrade. Air conditioning the trains was out for two reasons: no space on the trains plus the heat generated from the air conditioning would simply sit around in already hot tunnels with nowhere to go, making things worse.

We innovated using cold ground water to cool air at stations...and invested in 13 ventilation shafts to suck in cooler air

We took a systems solution, starting with two simple requirements of reducing heat at source and increasing circulation of cooler air into the system. We innovated with using cold ground water to cool air at stations, starting with Victoria station then moving to Oxford Circus and Green Park. We also invested in 13 upgraded and new ventilation shafts along the line to suck in cooler air and allow the "piston" effect of the tube trains (that's how they're shaped if you look at them end-on) to push this newly introduced air around the system. And during hot weather, our assets also require special attention. For example, track needs to be specifically prepared for high temperatures through thorough review of condition records and, if necessary, additional work on joints and stresses within long welded sections.

 The final part was system-engineering the train control system. This included providing far more sophisticated control for the regenerative braking, which recycles energy from a train as it slows down, to be used by others as they accelerate, than we have used before. The end result is a line that feels decidedly cooler despite an increase of over 30% in capacity. 

Countdown to cold

Cold weather is another threat to service due to freezing of moving parts and ice and snow on the infrastructure. Over time we've developed a winter weather plan that, based on forecasts, starts a 5/4/3/2/1 day countdown with specific actions on de-icing track and points, preparing train depots to keep doors cycling, and additional measures at station platforms. Over time it's become a well-oiled plan and only rarely do we now see any discernible impact of cold weather on service. It's all about keeping to the plan!

Future- proofing of infrastructure is a subject we as engineers need to engage in and explain more, in my view.

Targeted flood investment

Finally, to flooding. London, of course, is protected by the Thames barrier (and what a good long-term infrastructure investment that was) but our system is still vulnerable. We have over time built up a hydraulic model of our network, risk-assessed potential weak points, and made targeted investment  in pumps (often duplicated for redundancy and remotely monitored), new drainage, innovation and looked again at our design criteria for what size of storm to allow for in future! The result is that despite the intense and prolonged rainfall of the last few months, there has been very little impact on our service.

 Future- proofing of infrastructure is a subject we as engineers need to engage in and explain more, in my view. Take the Jubilee line stations for example. These were sized to cope with capacity growth over the next hundred years and had to be justified against the background of the harsh economic recession in the 90s. Yet who would now say for example that Canary Wharf station is too big - and that's only 15 years in!

 If drainage is historically designed for a rainfall intensity that comes along once every say 75 years, then it will obviously flood if a rainfall intensity far greater – say once in 200 years – comes along. So hard decisions need to be made now about how large (and how expensive) our drainage systems are. We face similar debates on railway capacity and power.

 These are all very long-term decisions and those who make them are rarely around to reap the benefits but all the historical evidence, going back to the wonderful Victorian engineers, says deign big and design long, like the Thames Barrier and the Jubilee line stations!