WASHINGTON (Reuters) - U.S. pedestrian and bicyclist deaths rose in 2018 while overall traffic deaths fell 1% in 2018 to 36,750, the National Highway Traffic Safety Administration (NHTSA) said in a preliminary report Monday.

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The auto safety agency said it did not know the cause of the overall decline but has said a dramatic increase in traffic deaths in 2016 was the result of more people killed on foot, bicycle or motorcycle.

In 2018, the agency said pedestrian deaths were projected please to rise 4 percent and bicyclist deaths by 10 percent. The overall traffic fatality rate was projected to drop to 1.14 deaths per 100 million miles traveled as deaths fell to 36,750, the lowest rate since 2014. Pedestrian deaths accounted for 16% of all U.S traffic deaths in 2017, up from 12% in 2009.

The agency has been investigating the role of distracted drivers in overall U.S. traffic death figures but has found challenges in getting an accurate picture of all distracted crashes because of the unwillingness of individuals to acknowledge they were distracted.

NHTSA said in 2017 there were 599 pedestrians, bicyclists, and others outside vehicles killed in distraction-affected crashes.

NHTSA counts fatalities as any death resulting from a crash within 30 days of the incident and it takes a lengthy review of several data sources before final numbers are published.

The increases in deaths among pedestrians and bicyclists come after a 1.7% decline in pedestrian deaths in 2017 to 5,977 and an 8% decline in bicyclist deaths to 783.

The issue remains a big concern in large U.S. cities.

In New York, pedestrian deaths accounted for 46% of the city’s 207 traffic deaths in 2017, while 60% of the 15 traffic deaths in San Francisco were pedestrians.

Overall, traffic deaths in urban areas are up 17% since 2008. They have fallen by 18% in rural areas.

Deaths of people inside vehicles, which in 1996 accounted for an all-time high of 80% of all traffic deaths, has fallen to 67% in 2017. The 33% outside vehicles figure includes pedestrians, bicyclists and motorcyclists.

The fatality rate and number of deaths is down dramatically from 2007, when 41,259 people were killed and 1.36 deaths per 100 million miles were recorded.