Parents of two teenagers killed on major thoroughfares in Nassau joined County Executive Edward Mangano and other officials Tuesday to announce the placement of their 13-minute "walk safe" video on YouTube.

"It was a lengthy process preparing for it [the video] and dealing with it afterwards," said Kelliann Davis, of Long Beach, who took part in the video. Her younger sister, Lauren Davis, 18, died after being struck crossing Hempstead Turnpike near the Wantagh Parkway entrance in 2009.

In the video, Davis recounts her family's decision to let Lauren die so her organs could save the lives of three others.

Sandi Vega of Wantagh, whose daughter, Brittany, 14, was killed crossing Sunrise Highway in 2010, also participated in the video and Tuesday's news conference in Mineola.

Mangano praised "the strength and resilience of family members" who "managed to turn some of their unimaginable grief into positive advocacy."

Vega later said she had lobbied hard for the "complete streets" program that says roads should be built with all users in mind, not just drivers.

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Gov. Andrew M. Cuomo signed the Complete Streets Act in 2011, "requiring state, county and local agencies to consider the convenience and mobility of all users when developing transportation projects that receive state and federal funding," according to the state Department of Transportation website.

"You would think that bit of common sense was always part of the law, but it wasn't," county Legis. Dennis Dunne (R-Levittown) said.

Mangano said that from 2005 to 2011, two to seven people a year were hit and killed on Hempstead Turnpike's 16-mile stretch, and between 2009 and 2011, a total of 13 were killed.

He started his Walk Safe Nassau public education campaign in May 2012 to encourage walkers to cross the turnpike at intersections, and "with caution" he notes no pedestrian fatalities have occurred on the turnpike since then.

"And with fewer accidents on it," said Chris Mistron, Nassau's traffic safety chief.

Mangano had the yellow push-button box on display, and said, if pushed, it gives a pedestrian about four extra seconds before the light changes.