When the guidelines reached the Senate late last year, it reportedly didn't include trucks -- far from ideal, considering quite a few companies are already working on autonomous big rigs. Daimler tested a platoon of them in Oregon, while Toyota and Volkswagen joined a full-scale autonomous truck platooning trial in Singapore. Uber began developing autonomous trucks after its controversial purchase of Otto, a company founded by a former Waymo engineer who allegedly stole the Alphabet company's self-driving technology. Tesla has recently unveiled a truck with semi-autonomous features, as well.
Automakers have been asking the government to make changes to vehicles' safety standards for a while now, so that they don't have to meet all 75 of them to be able to start deploying their fully autonomous products. Most of those standards don't apply to cars without steering wheels and pedals anyway. They've also been asking the administration for favorable laws that apply to all states, preventing individual states from blocking autonomous vehicles on their roads.
We might only have to wait a bit to start seeing level four or five autonomous cars on the road once the new rules are in place. GM recently detailed its plans to release a no-steering-wheel, no-pedal car in 2019, and its rivals will likely follow suit.