Remember those unexplained voltage spikes that knocked over 100 BART cars out of service earlier in the year? Thankfully, whatever was causing the disruption eventually stopped, and BART was able to resume normal service in April. There's just one, tiny outstanding issue: Officials still have no idea what caused the voltage spikes in the first place, the Chronicle reports, despite spending over $2.5 million in an effort to diagnose the problem.

“The issue has completely gone away, and we have fully recovered from it in terms of our our car count,” BART spokeswoman Alicia Trost told the paper. “But we still need to find out what caused it so it doesn’t happen again.”

The trouble began/manifested in late February, when train cars passing east through the Transbay Tube began to short out. Shortly after, a similar shorting out started happening between the North Concord and Pittsburg-Bay Point stations — forcing BART to run a bus bridge. And so, as one would expect, BART officials went to work to determine the root cause of all the problems.

Unsurprisingly, that work cost a lot of money. Let's break that $2.5 million down:

  • $200,000: The amount spent on "outside consultants" to search the electrical systems.
  • $800,693: Labor, including repair work.
  • $332,449: Replacement parts.
  • $771,703: Test equipment.
  • $134,472: That aforementioned bus bridge.
  • $265,000: The projected amount of lost fare revenue.

Oh, and according to Trost, those numbers might still go up. “There could be more costs if the data team comes back wanting more testing,” she told the paper.

So, rest assured that while the BART electrical problems may not be ongoing, associated expenditures still are.

Related: BART Chaos Continues As Riders Revolt On Twitter