Delays piled up on the subway tracks over the past two years, with the F line getting hit with the most incidents, according to a Straphangers Campaign analysis.

The group's report, with findings based on MTA text and email alerts, shows that last year's spike in delays -- up 35% from 2011 -- was mainly caused by mechanical problems and incidents with track and signals. There were 3,998 alerts pushed out to riders in 2013, according to the report, which excluded uncontrollable delays such as sick passengers and police activity.

Riders on the F train -- the line that saw a derailment last week in Queens -- had 326 incidents, while L train passengers saw the biggest increase in delays, which nearly doubled to 183 last year from 96 in 2011. The J and Z trains had the fewest number of significant incidents and were the only train lines to see a decrease from the 2011 study. There are no 2012 numbers due to Superstorm Sandy's impact on the system, which is still affected by the flooding that occurred.

"There's a very substantial increase of what they call incidents," said Gene Russianoff, staff attorney for the Straphangers Campaign. "That's not good."

The MTA, however, said in spite of delays and problems from Sandy, riders are not waiting any longer on the platform than they did in 2011, according to its own measure of all delays. The MTA's latest assessment of wait times shows the agency is meeting its goal of nearly 80% of trains meeting the standard for arriving at a station from March 2013 to February. "Despite increased ridership and the challenges we face with these incidents, we continue to develop and deploy strategies to maintain even intervals of service for our customers, and our wait assessment metric reflects this focus," said MTA spokesman Kevin Ortiz.

The MTA also said additional staff was added to get electronic alerts out in shorter amounts of time and that the Straphangers report overstates delays if an incident affects lines that share tracks. The alerts are also initial reports to help passengers plan their trip and that they are an unreliable metric for service, according to the MTA.

But Russianoff said the delays seem to be growing in a transit system that is reaching its most crowded levels in decades.

"It's inconceivable to me that what's going on here is that they've just gotten better at pushing out these announcements," Russianoff said.

The electronic alerts go out to more than 100,000 riders when an incident is expected to impact service for 8-10 minutes or longer, according to the agency.