Tesla is adopting a take-it-slow approach to the rollout of its next-generation Autopilot system, in an effort to balance safety against its race to put advanced self-driving technology in the hands of its customers. A Tesla spokesperson confirmed to The Verge that customer safety is the primary reason behind Tesla’s slow deployment of Autopilot features and Elon Musk himself advised owners to exercise caution when using Autopilot when part of the system was rolled out over the weekend.

Back in October, Tesla rolled out a suite of more advanced sensor hardware in its cars — radar, cameras, and an onboard “supercomputer” — but the software that makes the safety and driver assist features work wasn’t yet complete. As a result, Tesla vehicles (the Model S sedan and Model X SUV) built since then have many fewer safety and convenience features (everything from rain-sensing windshield wipers to the Autosteer feature that most consider to be “Autopilot”) than those available in older models.

The idea is that while its cars will be more capable in the future, they aren’t quite there yet. Once Tesla finishes developing the software, the newer cars will have more advanced driver assist systems and, Tesla says, cars purchased today will eventually be able drive autonomously in all situations. But for now, it means that older Tesla cars have more safety and convenience features than its newer cars.

Tesla CEO Elon Musk calls the new sensor suite “HW2,” an acronym for second-generation hardware, and the software is called AP2. Tesla considers the entire suite of safety and driver assist features to be the Autopilot Safety Features, though the Autosteer and traffic-aware cruise control features are what most people consider to be “Autopilot.”

After a Tesla driver was killed in a crash with Autopilot active last year, Tesla unsurprisingly chose to handle the rollout of AP2 with an abundance of caution. The company is validating its software “from the ground up,” and this past weekend, Tesla rolled out a speed-restricted version of its Autopilot driver assist software for Tesla cars equipped with HW2. However, even with that update, new Teslas are still missing a ton of features including blind spot monitoring and and automatic emergency braking that are available in HW1-equipped cars built between September 2014 and October 2016, and which are table stakes for most luxury cars. (See the bottom of this article for a comprehensive list.)

Tesla validated the first version of Autopilot silently for months, running the software in “shadow mode,” testing in the background and allowing the company to check its work without actually taking control of a car. AP2 is currently being tested the same way. The goal is to verify that the system functions as expected. Over the weekend, Elon Musk advised owners to “be cautious” when trying out the new HW2 Autopilot features.

Extensive testing is a good thing, but the downside is a slow rollout of Autopilot safety and convenience features. Tesla’s website still promises a December 2016 rollout of “Enhanced Autopilot,” a next-generation of Autopilot that is more capable than Autopilot 1, promising the ability to automatically transition from one freeway to another, or for the car to autonomously park itself in a parking lot or garage. But Tesla is behind schedule because it doesn’t want to introduce Autopilot software that isn’t ready.

In its investigation of the fatal Autopilot crash, NHTSA said the crash rate of Tesla cars dropped by 40 percent after Autopilot was installed, validating Tesla’s claims that the feature is safer than human driving. The investigation also cleared Tesla and Autopilot of any fault for the crash, noting that the driver should have had at least seven seconds to react and try to avoid the crash. Tesla has worked to keep drivers from abusing the system, and a software update last fall made Autopilot more insistent in an effort to keep the driver’s attention on the road.

As Tesla polishes its software, it will loosen the reins on what drivers can do. Tesla will raise the speed limit on Autopilot, currently 45 mph, “as we get more data,” said Musk, also revealing that the autonomous capabilities on Hardware 2 will improve every two to six weeks via over-the-air updates. The missing features, it seems, will show up — eventually.

Tesla is no stranger to slipping schedules, but it seems the company is delaying the updates of Autopilot for the right reasons: because it’s not ready yet. But Tesla buyers seem unphased: the company delivered 22,200 vehicles in the fourth quarter of 2016, even though (or perhaps because) all of those cars have a promise of future technology, rather than having it today.

Update 06:25PM ET: The headline of this article has been changed to avoid suggesting that there is a particular safety issue with Autopilot.

For reference, below is a list of safety features currently available on Tesla cars with HW2/AP2 (built after October 2016), as well as features currently available only older Teslas equipped with HW1/AP1 (built between September 2014 and October 2016).

Features available on Hardware 1 and 2:

Low-speed Autosteer: It maintains the vehicle’s position within a lane and allows the driver to briefly remove their hands from the wheel in some situations. Restricted to 45 mph and below (on HW2).

Traffic-aware cruise control (TACC): Maintains and adjusts vehicle speed to match the vehicle in front, accelerating or decelerating as necessary. When Autosteer and TACC are used together, Tesla classifies the system as SAE Level 2 on the autonomous scale. Restricted to 75 mph and below (on HW2).

Forward collision warning (FCW): A system that warns the driver of an imminent frontal collision with audible and visual warnings.

Blind spot warning (BSW): Alerts the driver when a vehicle is in the car’s blind spot.

Speed assist: Vehicle can read and display speed limit signs to the driver.

Automatic headlamps: Turns on the headlights automatically when it gets dark.

Features available on Hardware 1 (not yet available with Hardware 2):

Automatic windshield wipers: Activates the wipers when it rains.

Automatic high beam headlights: Turns the high beams on and off automatically.

Automatic emergency braking (AEB): Can automatically apply the brakes to avoid or reduce the severity of a crash.

Side collision warning: Alerts the driver when a collision with a vehicle in the adjacent lane is imminent.

Lane departure warning (LDW): Alerts the driver when the car leaves its marked lane without a turn signal active.

High-speed Autosteer: Autosteer at speeds above 45 mph.

Auto lane change: An Autosteer feature where the car can change lanes on its own when the driver activates the turn signal on a multi-lane road.

Autopark: When activated, the car can steer itself into a parallel or perpendicular parking space.

Summon: The car can pull in and out of parking spaces, without a driver in the car, when a button is held on the key.