Runway safety improvements under way at SFO (pictures)
Two of four runways will close as part of federally mandated improvements. CNET takes a look at the technology and gets a tour of SFO's runways.

Now arriving
Two commercial passenger jets prepare to land on parallel runways 28L and 28R at San Francisco International Airport on Thursday, March 20, 2014.
Under construction
Construction work has already begun on the Runway Safety Area (RSA) at one end of Runway 1 Left, though the heavy work will begin when the runways are closed in May.
Lining up
An aircraft lines up for departure on 1 Right, which will also close until September. In the background is SFO's new control tower.
Close to your car
Here you can see just how close the affected runways are to the 101 freeway that borders the airport.
Airport overview
A map of of SFO showing runway locations and the new taxiways. The new EMAS materials will be installed in the green areas.
For your safety
The EMAS technology works like a runaway-truck ramp for airplanes, collapsing to assist in the slowing of planes that might overshoot the runway.
Engineered Material Arresting System
The EMAS material that will be installed collapses on impact, slowing a plane that has gone off the runway.
Installation areas
The EMAS tiles will line the beginning and end of Runways 1 Left and 1 Right. Here you can see where they will be installed next to San Francisco Bay.
Arriving from Amsterdam
Across the field, a KLM MD-11 arrives from Amsterdam.
Stop!
As we toured the airport's perimeter, signs like this one warned us when we were about to cross a runway's end.
Air China Boeing 777
An Air China Boeing 777 passes over the Runway Safety Area at the end of Runway 28 Right just before touchdown. The installation of these RSAs was completed last year.
Side by side
As an ANA Boeing 777 awaits takeoff clearance on 28 Left, a small private plane arrives on 28 Right. The construction closure means that all departing and arriving traffic will be restricted to these two runways. Close operation like this, however, will be permitted only in good weather.
Jet blast warning
Mind the jet blast.
Heading for Portland
A Portland, Ore.-bound Alaska Airlines Bombardier Q400.
On its way
Virgin America maintains its hub at SFO.
AA retrojet
American Airlines' retrojet pays a visit to SFO.
United Express Embrarer 120 Brasilia
A United Express Embrarer 120 Brasilia climbs out on a short-haul flight.
Boeing 777
A Boeing 777 taxis for departure to Korea.
Looming large
The 777 is one of the largest aircraft to operate at SFO.
New in town
Qatar Airways doesn't serve SFO, but one of its Airbus A340s was parked in a remote area.