King County and Metro Transit described Monday’s shooting of a bus driver and the subsequent boarding of another bus by the gunman as an anomaly in what they say is normally a secure transit system for drivers and passengers.

“This is not a transit issue,” King County Executive Dow Constantine said Monday. “Again, the transit system is safe.”

High-profile attacks on Metro drivers periodically grab headlines — from a teenager’s beating of a driver in 2010 to the last time a Metro operator was shot in 1998, causing a bus to plummet off the Aurora Bridge.

But assault figures appear to bolster Constantine’s words.

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In the mid-2000s, reported assaults on bus operators were escalating, from 125 in 2003 to 189 in 2006.

But since then, the numbers have decreased. Reported assaults on Metro operators dropped to 147 in 2009. Over the next two years, they fell even more dramatically — to 86 incidents in 2010 and 84 in 2011.

Reported assaults climbed back to 107 last year — but that’s still far less than they were even four years ago, Metro spokesman Jeff Switzer said Monday.

In the first half of this year, reported assaults on bus drivers systemwide totaled 52.

“Safety is a daily concern for us,” said Paul Bachtel, president and business manager of Amalgamated Transit Union Local 587. “But the numbers for these kinds of incidents are dropping because we have a good relationship with the King County Sheriff’s Office and Metro to address this kind of thing.”

In recent years, county and Metro officials have worked with the transit operators’ union to implement safety training programs and test safety equipment, among other actions, Bachtel said.

After a 14-year-old attacked a 56-year-old woman who was driving the 124 Metro bus in Tukwila in January 2010, Metro launched a pilot program that installed driver safety shields on some bus routes. The plexiglass partitions that enveloped the driver’s area restricted contact between operators and passengers.

But following more research of the prototypes and conducting a survey of 300 drivers who tested the shields in the field, the union’s executive board ultimately recommended not to install the shields systemwide, Bachtel said.

“Our drivers felt it would only make their relationships with the passengers worse,” he said.

Even the shields had been in place, Bachtel noted they couldn’t have prevented Monday’s shooting. The shields aren’t bulletproof, he said.

King County and Metro authorities said they’ve also tried to focus on beefing up safety policies and policing tactics in recent years to help increase security.

All Metro operators undergo a safety-training course with police when moving into full-time positions, said Metro operations manager Jim O’Rourke. Over the next three years, a refresher course is also planned for all drivers, whether full or part time, he added.

Among other tactics, such training teaches drivers to diffuse potentially hostile situations.

“We call it, ‘Don’t take the bait,’ ” O’Rourke said. “If someone’s getting emotional or acting aggressively, we tell our drivers not to engage. In some cases, it’s about depersonalizing the situation by saying, ‘Oh, Metro policy states this …’ ”

O’Rourke said the overall goal is to limit the number of assaults on drivers to less than 10 per year.

King County sheriff’s Major Dave Jutilla, who heads the Metro Transit Police Department, said his agency has stressed faster response times in recent years. Jutilla noted two transit-police supervisors and four to five line deputies responded to Monday’s shooting within four to five minutes of the initial emergency call.

Metro also has added new camera systems near bus stops and at transit centers, launched programs to reward crime reporting and suspend bad-behaving passengers, and lobbied for tougher laws in Olympia, he said.

Now, under state law an assault against a bus driver — just like an attack on a police officer, firefighter or several other professions — is a felony that carries stiffer penalties.

Since 2011, King County prosecutors have charged 32 adults with third-degree assault under the provision, prosecutor’s office spokesman Dan Donohoe said Monday.

Lewis Kamb: or (206) 464-2932. Twitter: @lewiskamb