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The National Highway Traffic Safety Administration has again delayed adoption of rear visibility rules that would require backup cameras in all passenger vehicles sold in the US. It's the fourth delay in a string of setbacks dating to 2007. That's the year Congress passed legislation intended to improve rear visibility in new vehicles.

NHTSA legislation had previously required automakers outfit at least 10 percent of their cars with backup cameras by 2012, 40 percent by 2013 and 100 percent by 2014. Those deadlines will likely be changed now. Delays have been blamed largely on automakers' arguments that the new requirements will be too costly. Estimates suggest that MSRPs on vehicles already outfitted with display screens would need to increase an estimated $58-88, while models without would see price bumps of between $159 and $203.

The agency estimates that the new regulations could have cost the industry between $700 million and $1.6 billion by 2014. According to The Detroit News, "NHTSA uses a statistical figure of $6.1 million as the value of a human life and says under a best-case scenario, the proposal will cost between $11.8 million and $19.7 million per life saved."

The government agency has not yet announced if or when a new deadline will be set.