Design Elements of Performance

An equipment spec used to look like the Yellow Pages (and sometimes they still do). Part of the reason behind this was that agencies dictated down to the nuts and bolts, literally, how their equipment was to be designed. Sure, this gave them control over the process, but this spec micro-management also left them responsible should anything go wrong with their equipment. It allowed suppliers to say, “Well, we did what you asked us to.”

Performance Base
In an effort to provide the best equipment possible for their customers, many agencies have shifted toward or wholly adopted a performance-based spec process. With a performance base the spec states what the agency wants the equipment to be able to do, not exactly how to do it, allowing the supplier to determine in their opinion the best way possible to accomplish this task.

“For vehicles, for just about anything, we try to do performance based. That’s not to say if you look that 100 percent of what we do is performance based, but that’s preferred,” says Andrew Murphy, equipment engineer for Austin’s Capital Metro.

“I guess it’s sort of like, I’m not in the business of designing a bus. I mean, I could be, but I don’t know the latest technologies, I don’t know the most recent materials that are out there, I don’t know the most economically advantageous manufacturing techniques.”

Murphy explains that in a recent process to purchase some paratransit vehicles, he was looking at getting an air conditioner that would cool the bus sufficiently. Rather than tell them exactly what he wanted, he just wanted it to cool the bus. When asked how many BTUs he wanted, Murphy said he didn’t know, he just wanted it to cool the bus, explaining that if he required a certain amount of BTUs and was wrong, he could have a vehicle that fit his spec, but not do what he wanted it to. By giving a performance-based spec, there is an implied warranty that the equipment will perform as the agency has requested.

“If the air conditioning doesn’t cool the way I want it to, [the supplier] could point out that they put everything physically into it that I told them to. And they put the screws in where I told them to and everything. But then when it doesn’t cool, I have no recourse. Here if there is a problem, if it’s with an air-conditioning system or some other mechanical component, the warranty is on the performance, if you would, in addition to the individual components. In other words the bus needs to cool, the bus needs to run or the bus needs to start or do whatever it needs to do.”

Murphy says that he has seen a significant change in the last five to eight years in the way his agency has done speccing. Where they used to use the tried-and-true design-based philosophy, now they are almost entirely performance-based. Why?

“I think there’s been a variety of factors and the most obvious might be that there’s nothing worse than having a problem with your bus and realizing that it was built to your specification, but that your specification was maybe wrong,” says Murphy. “Or that the people that wrote the specification at the time didn’t fully understand what it was that they were writing.”

Murphy says that many design-based specifications actually come from the suppliers themselves. Agencies then copy the ones they like into their specs, but human error can crop up and cause an important part to be left out. Using a performance-based spec, the agency can simply say they want a product to last a certain number of years and be resistant to wear and let the supplier figure out how to accomplish that.

Murphy says design is difficult as you can easily overlook something, whereas with performance, “…it is sort of a black box thing, I just want to put something in this side of the black box and I want this thing to come out of the other side of the black box, I don’t want to have to worry about what happens in the middle there.”