The National Highway Traffic Safety Administration on Thursday officially signed off on a new self-driving vehicle from the delivery startup Nuro. It's a historic move; Nuro says it's the first time NHTSA has exempted a self-driving vehicle from regulatory requirements that apply to conventional vehicles.

Nuro's new delivery vehicle, the R2, looks a lot like its predecessor, the R1. Nuro has partnerships with Walmart, Domino's, and Kroger, and it has been using R1 robots to deliver groceries, pizza, and other products in the Phoenix and Houston areas since late 2018. But the R2 comes with some key improvements. The cargo area is significantly larger without increasing the overall size of the vehicle. And the R2—unlike the R1—has the ability to heat and cool the compartments to keep products at the perfect temperature.

The R2 is also notable for the features it doesn't have.

Cars in the US are governed by a fat book of NHTSA regulations called the Federal Motor Vehicle Safety Standards. These rules govern everything from the strength of the brakes to the inclusion of airbags and back-up cameras. Car companies must certify that they comply with these standards before they can introduce a new car onto the market.

But not all of the requirements make sense for a self-driving car. For example, the FMVSS requires cars to have side mirrors that are useless to self-driving software. The FMVSS requires a car to have a windshield, which makes no sense for a small vehicle that only carries cargo.

So Nuro asked NHTSA to allow it to deviate from the standard in three ways. It wants to eliminate the mirrors and replace the windshield with what Nuro's CEO describes as a "specially designed panel at the vehicle's front that absorbs energy, better protecting pedestrians."

Finally, Nuro asked NHTSA to waive a rule requiring a vehicle's rear-facing camera to turn off when the vehicle is moving forward. This rule is designed to prevent the rear camera view from distracting a driver, but that makes no sense for a software-controlled vehicle. As a condition of the exemption, NHTSA is requiring Nuro to report to the agency about the operation of the R2 and to conduct public outreach in areas where the robot is used.

While Nuro is the first company to get a specific exemption for a self-driving vehicle, it's far from the first company to put self-driving vehicles on the roads. So how did other companies do it? Rather than seeking exemptions from the FMVSS, most have found it easier to just comply with the existing requirements—even ones that add no value for a self-driving car. Alphabet's Waymo, for example, has repurposed Chrysler Pacifica minivans for its self-driving fleet. Pacificas already meet FMVSS requirements, so as long as Waymo leaves its safety features in place, the company doesn't have to worry about compliance. This is why Waymo's vehicles—even those with no safety driver—have steering wheels, pedals, mirrors, and other equipment that passengers aren't allowed to touch.

NHTSA has a lot of work ahead of it

To get an exemption, Nuro had to demonstrate that its vehicles would be at least as safe as vehicles that fully meet the FMVSS requirements. Windshields and mirrors are completely useless to self-driving software, and if anything, turning off the rear camera makes self-driving software less safe. So it wasn't difficult for Nuro to make its case.

NHTSA's Thursday's decision represents just the first of several steps needed to rationalize regulation of self-driving cars. Nuro's new exemption allows Nuro to manufacture and deploy up to 5,000 vehicles over the next two years that lack mirrors and windshields. But the law allowing NHTSA to grant these waivers limits how many vehicles they can cover, so it's not a long-term solution for Nuro or other companies hoping to reach national scale.

Thursday's waiver is also limited in another important way: the R2 is classified as a low-speed vehicle limited to 25 miles per hour. This category is attractive for self-driving car companies because fewer FMVSS rules apply to low-speed vehicles than full-size vehicles. But Nuro wants its vehicles to eventually travel faster than 25mph. Higher speeds trigger more safety requirements. For example, faster vehicles need airbags.

David Estrada, Nuro's chief policy officer, tells Ars that NHTSA has begun working on a new regulatory category specifically for zero-occupant vehicles like the R2. He's optimistic that NHTSA will be able to craft these new rules fairly quickly. In Estrada's view, all NHTSA needs to do is go through the rules for conventional cars and delete requirements that no longer make sense—things like steering wheels, mirrors, and airbags. Other rules—like those governing a vehicle's brakes, headlights, and turn signals—could be left as-is.

Of course, NHTSA might consider introducing some new safety requirements as well as deleting irrelevant ones. For example, a human-driven vehicle inherently has a human being monitoring it and ready to intervene if something goes wrong. That's not necessarily true for a zero-occupant delivery vehicle. So NHTSA might want to put in place safeguards to ensure that zero-occupant vehicles (and fully self-driving taxis, for that matter) get adequate remote monitoring from their human owners.

In principle, NHTSA could go much further. The agency could establish performance standards for the sensors in self-driving cars or even establish a comprehensive framework for testing and certifying self-driving software. However, establishing such rules this early in the process could easily backfire, locking suboptimal technologies in place or slowing down the pace of progress.

In 2018, Congress came close to passing legislation designed to speed up NHTSA's overhaul of self-driving regulations. It would have dramatically increased the numeric cap on short-term exemptions while pushing NHTSA to accelerate its overhaul of safety regulations. But the proposal ultimately did not become law. Some members of Congress launched another effort last year, but it hasn't gained much traction.