With more than 75,000 Super Bowl fans packed into NRG Stadium mere blocks away, an all-too-common Houston tragedy played out at a busy intersection of people and trains Sunday when a man on a bicycle was killed after turning into the path of a Metro train. Days earlier, a Rice University professor was struck and killed by a train while cycling to work near the busy Texas Medical Center.

The two deaths highlighted a long-standing issue that transit officials and others in Houston have spent the past dozen years trying to address. Compared to its closest peers, Metropolitan Transit Authority's nearly 23-mile system has more collisions per mile between pedestrians, cyclists and trains than any other major line in the country, according to the National Transit Database, maintained by U.S. Department of Transportation.

The dubious distinction, however, comes with a number of caveats which Metro officials said are important to keep in mind.

"Each community and each system is different, and there are probably different factors," said Metro CEO Tom Lambert.

He noted Houston's system, unlike some others, has more at-grade street crossings and doesn't have the level of restrictions other systems have to keep trespassers off the tracks. That makes safety a larger part of Metro's day-to-day challenges, he said.

"We've always looked at how do we continuously improve things," he said.

Still, two deaths since Friday morning - the ninth and 10th of pedestrians or bicyclists along the tracks since 2004 - highlights the simple fact the trains can be deadly.

On Friday morning, Rice University physics professor Marjorie Corcoran, 66, was killed as she pedaled to the campus. Metro officials said Corcoran crossed over the southbound tracks along the 6300 block of Fannin near Sunset in front of a passing train.

10th fatality since 2005

Sunday night as spectators packed NRG Stadium for Super Bowl LI, a man riding a bicycle in the opposite direction on the eastbound Loop 610 frontage road turned left onto the northbound tracks. He was struck by a train. He later died at Ben Taub Hospital and has not been identified.

Of the 10 fatalities, half have been pedestrians, four were bicyclists and one - the system's first in 2005 - was driving an automobile.

Since 2004 when the original 7.5 miles of the Red Line opened, the train has been a source of tension and frustration for drivers. Though many lament the loss of block after block of left turns from Main, others have always questioned the safety of having trains intersect with vehicle traffic.

Incidents are common enough that critics have for years called the line the "danger train" because of its role in accidents.

As the mileage of light rail in Houston has grown, so have the number of collisions. In 2014, before the Green Line and Purple Line opened, Metro reported 58 collisions. Last year, the number of collisions jumped to 108, though many were along the Red Line.

Houston streets generally are becoming a more dangerous place, according to various data sources. Automobile crashes, fatalities involving bicyclists and the number of pedestrian crashes all increased at least 10 percent from 2014 to 2015.

Yet it is the trains that take a huge amount of scorn from many drivers.

"I know so many people who say it terrifies them," said Scott Smith, 44, who works in Midtown. "Every place else, it's not in the street."

Many cities, however, mingle the trains and cars, though it's difficult to assess how much of Houston's system is open than others. Lambert said certainly a system that shares the road and more crowded areas will have more collisions.

Officials, in developing Houston's rail plan roughly two decades ago, chose an at-grade system because of the enormous cost associated with subways and the cost and appearance of elevated rail. With few exceptions, at-grade light rail has been the norm in America for years, but few places outside Houston have built their lines in some of the most congested and pedestrian-heavy areas of their respective urban regions.

More safety measures

Lambert stressed that doesn't absolve Houston officials from looking for options or not aiming for similar safety standards as closed systems.

"We should not say that anything is off the table to look at, but at the same time we need to study the consequence of any change we might make," he said.

Metro has made changes both to on-street infrastructure, such as traffic signals and their outreach efforts to preach safety. To reinforce red lights along the line, Metro developed an LED red band around traffic signals to be an extra level of visibility for drivers.

Transit officials also worked with Houston Public Works on downtown traffic light timing to give trains a head start to reduce abrupt turns in front of trains.

Crews also fenced off areas near Loop 610 and the Red Line - the location of Sunday's fatal wreck - to reduce panhandling in the area. Signs were also hung warning pedestrians about the train, and the audible bells for the mechanical gates that lower when trains pass along Fannin were changed to ring the entire time the gates are down, Lambert said.

As supporters of the line often note, education and awareness by drivers, cyclists and pedestrians is the most effective way to reduce crashes.

Investigations of every fatal collision involving Metro trains since 2004 found the crashes were non-preventable, meaning there was nothing the train's operator could have done to avoid the crash.

All were the result, ultimately, of someone turning into the path of the trains, unaware of their presence.

Still, bicycling advocates said there is good reason to look at both design of Houston's streets and the tracks and educational opportunities.

"The answer isn't quite as simple as 'don't cross in front of a train,'" said Mary Blitzer, advocacy director for BikeHouston.

Cyclists ask for plan

Along with common sense when riding or walking, such as looking both ways and refraining from using headphones around the trains, Blitzer said road design and options should be improved so cyclists can avoid certain situations.

"Our initial response to these deaths is to ask why people are in unsafe places," she said, citing Sunday's death as an example because the rider was using the frontage road and tracks. "There are many answers to this, but one answer is probably there aren't any safe roads across 610 in this part of town."

Bicycling advocates are currently urging city officials to review and pass a master plan for improving bike facilities in Houston. City Council's transportation, technology and infrastructure committee is scheduled to discuss the bike master plan Monday before it moves onto the full council, potentially by the end of February.

"An implemented bike plan would limit exposure to the dangerous roads because you have a network of safe places to ride," Blitzer said.