What will the capping of the BP (NYSE: BP) well mean for energy-related exchange-traded funds? And which transportation-related ETFs should investors consider taking out for a spin? I recently asked ETF Database analyst Michael Johnston.

Mac Greer: All signs are that BP has capped the well and is working on the final solution as we tape this interview. What ETFs stand to benefit from BP capping the well?

Michael Johnston: This whole scenario has put a lot of focus on what Washington is going to do and what the regulatory response is going to be to the oil industry. If BP is able to cap the well, this starts moving to backs of people's minds as they move on to the next story and there is not quite the pressure to crack down on big oil. So I think funds like the Energy Select Sector SPDR (NYSE: XLE), which does not have any exposure to BP, could stand to benefit because the firms that are in this ETF -- ExxonMobil (NYSE: XOM), Chevron (NYSE: CVX), etc. -- are maybe not going to be subject to the same scrutiny that they would have been otherwise if this had dragged on.

Another interesting one is the Oil Services HOLDRs (NYSE: OIH).  This is an ETF that includes the companies that are probably going to be affected most by any potential regulatory reform that includes a ban on deepwater drilling. So to the extent that Washington is able to ease back a little bit and doesn't quite feel the pressure to crack down so hard on the oil industry, those are two ETFs that could be a beneficiary that despite the fact that, again, they don't hold BP in their underlying holdings.

Greer: And Michael, you recently wrote an article ETF Plays on Planes, Trains, and Automobiles.  What are some ETFs that play on transportation, and specifically, planes, trains and automobiles?

Johnston: I think one interesting one is the iShares Dow Jones Transportation Average Index Fund (NYSE: IYT) which owns a number of railroads, a number of competitors now to BNSF, as well as other aspects of the transportation industry, including trucking and companies like FedEx (NYSE: FDX). I think those are fascinating plays right now because it is a way to isolate the U.S. economy. We are in a time where the global economies are more interconnected than ever before.  But the roads end at the ocean and the train tracks end at the ocean, so the railroads and the trucking companies are kind of immune to what is going on in Europe. And they don't care what is going on in China and they don't care what the latest out of Australia is. They are more of a pure play on the U.S. economy.

A couple of other related funds -- FAA is the Claymore Airline ETF, which is kind of a fascinating sub-industry that has been always in the headlines and always exhibits quite a bit of volatility and again, is almost a leveraged play on the need to get things from point A to point B, which in turn is a function of the overall economic environment. SEA is the shipping ETF, which again is the same general investment thesis. If things need to be moved from point A to point B, shipping is a common way to do it and to the extent that that need picks up, the profitability and the outlook for the shipping industry is something that may pick up quite a bit.

Mac Greer doesn't own any of the stocks mentioned.

FedEx is a Motley Fool Stock Advisor pick. Chevron is a Income Investor recommendation. The Fool owns shares of ExxonMobil. Try any of our Foolish newsletter services, free for 30 days. The Fool has a disclosure policy.