Daimler Trucks North America raised a few eyebrows when it announced at the CES electronics show in January that the next generation of Freightliner Cascadia would be able to steer, brake, and manage vehicle speed without input from the driver. That meets the definition of Level 2 autonomy as defined by the Society of Automotive Engineers.
As a driver assistance system, vehicles at Level 2 can simultaneously steer, brake and manage speed without driver intervention for short periods, but the driver must remain attentive and be prepared to regain control of the vehicle at any time — unlike several now-infamous Tesla drivers who put a little too much faith into that Level 2 system.
Daimler has baked these features into the latest version of its driver safety suite, Detroit Assurance 5.0 (see page 50). Active Brake Assist uses “fused” radar and camera technology to provide emergency full-stop braking capability without action from the driver. ACC to Zero (Adaptive cruise control to 0 mph) provides full acceleration and service brake capability from any set cruise speed down to a full stop, and it can launch again after the full stop if the interval doesn’t exceed a couple of seconds. As with previous generations, ACC maintains a set following distance from a vehicle ahead of the truck based on a pre-set time interval (2.4 to 3.6 seconds).
The active steering features, called Active Lane Assist, in Detroit Assurance 5.0 are optional, and include Lane Keep Assist (LKA) and Lane Departure Protection (LDP). When ACC is enabled, LKA uses micro-steering movements to keep the truck centered in its detected lane, based on the lane markings painted on the road.
Lane Departure Protection is active above 37 mph whenever ACC is not enabled. If the truck crosses out of its lane without the driver using a turn signal, an audible warning sounds alerting the driver to a lane departure. If the driver does not counter-steer and the truck continues to veer out of its lane, LDP will actively steer the truck back into its lane.
Steering control is provided by an adaptive power steering system from Bosch, called Servotwin. With this, an electric servo motor is built into the steering gear to assist with the steering effort and to steer the truck with torque input requests from the directional control system. That system takes lane position information provided by a windshield-mounted high-definition camera, processed by onboard electronics, and translates the data into movement of the steering column to maintain lane position.
Daimler says the Lane Keep Assist feature is intended to relieve the driver of some of the stress of steering the truck down the road. It makes minor steering corrections, just as a driver would, to compensate for wind drift, pavement geometry, vehicle alignment, etc., and it’s pretty good at it.
On Valentine’s Day, a little more than a month after DA 5.0 debuted in Las Vegas, I had a chance to try these new features at a media ride and drive event near Palm Beach, Florida. Unfortunately, the systems didn’t work quite the way they were supposed to (that happens; it’s new technology) that day, so a full and proper demonstration wasn’t possible. After some discussion with Daimler on what the underlying problem was (we never did figure it out for sure), the truck maker offered me a second drive so I could experience the system at its full potential. In late April I flew out to Daimler headquarters in Portland to have another go at it.
Lane Keep Assist
The optional Lane Keep Assist feature becomes active when the driver engages cruise control, in this case, Daimler’s adaptive cruise control. The driver also has the option of turning off LKA but leaving ACC operating. As I pressed the set button to establish my cruise speed, I felt a slight tug on the steering wheel as the Servotwin steering motor came to life. My initial instinct was to counter-steer, and I did, quite automatically, but then I relaxed my grip on the wheel and let the system take over.
I was accompanied on this trip by one of the engineers who designed the system, Sumanoharan (Suman) Narayanan, manager of advanced driver assistance and safety engineering at DTNA. He explained that the system makes requests for small amounts of torque input to the adaptive steering gear to get the desired front wheel angle. While the amount of torque will vary with the steering demand, it’s generally pretty light, and not at all difficult for the driver to resist if he or she wants to. I found I could easily over-power the automatic steering input if I wanted to, and of course I did just to prove it. I steered part way out my driving lane and when I eased the pressure on the wheel, it promptly but gently steered me back into the lane and straightened me out.
We drove about 100 miles that day, heading south from Portland, Oregon, along Interstate 5 to Salem, where we turned around and headed north again. That stretch of road is mostly straight with a few large sweeping curves. Curves can be challenging to the system, but I experienced no issues at 65 mph on those wide curves. It was a different story closer into Portland, where the road speed was lower and the curves a little tighter. Narayanan told me the tracking sometimes is lost on a tighter curve and the steering won’t hold the lane position, allowing the truck to drift out of the lane.
I experienced that lane drift a couple of times, but lower speeds improved the system’s ability to maintain lane position even in tighter curves. Narayanan told me the lateral acceleration in tighter curves or at faster speeds can sometimes be too much for the system, so it hands control back to the driver. When that happened, I felt a slackening in the wheel and I naturally, without even really thinking about it, steered the truck back into the lane. I also got an audible lane departure warning, but in these instances the Lane Departure Protection feature (more about that below) did not kick in because the ACC was still enabled (and the curve was too tight anyway).
Lane Departure Protection
Lane Departure Protection is another active steering feature. Upon sensing lane drift, it will counter-steer away from the direction of the drift to prevent the truck from leaving the lane. LDP is active only when adaptive cruise control is not on and LKA is accordingly disabled. With LDP, the truck will not self-center in the lane as it does with LKA. It’s meant only to prevent a lane departure, so upon counter-steering to prevent the drift, it heads for the opposite side of the lane, and once again counter-steers away from the newest lane departure threat. As a result, if the driver does not intervene and reassume control, the truck will ping-pong down the lane until the driver straightens out the truck.
Remember, LKA is not a self-driving feature. It was not Daimler’s intention to have this feature steer the truck without driver oversight. It merely assists the driver with the steering task, while providing some protection against inadvertent lane excursions.
With that said, Daimler has built in a warning system that detects when the driver is not applying some torque to the steering wheel. While I was driving, my hands were mostly just resting on the wheel, and the weight of my arms and hands seemed to be enough for the system to sense I was still there. To test the warning, I removed my hands from the wheel completely to watch the warning sequence.
Nothing happened for the first 15 seconds, then a yellow alert appeared on the dash display, with the words, “Hands On.” I ignored that, and after an additional 15 seconds, the alert turned to red, accompanied by a beep. The beeps continue every 5 seconds until a full minute has elapsed with no steering input from the driver. After 60 seconds, the beep becomes constant and the Lane Keep Assist feature is disabled, indicated by the blue steering wheel icon going out. If three such sessions are logged, the Lane Keep Assist is locked out until the next key-on cycle occurs — and the fleet is alerted that the driver is misusing the system.
Initially it felt odd to have the steering wheel moving on its own, and at first, I would counter-steer against the wishes of the truck. As my confidence in the system grew, I made a point of not counter-steering, to let the truck go where it wanted to go, and I must admit it did a good job of maintaining lane position (except in some curves). Narayanan told me that data collected from the test fleets clearly shows driver input to the steering is initially fairly high, but in a short time — a matter of hours in most cases — the test drivers relax and let the truck do its thing.
I had the lane-centering bias control set to center for the first half of the trip, and found on several occasions that the traffic to my left, which had a propensity to hug the right sides of their lanes, got a little too close for comfort. I eventually adjusted the bias control to the right, and my left-side space cushion increased enough to ease my concerns about trading paint with a passing truck.
The lane centering dropped off at one point while we passed through a section of poorly maintained lane markings. I heard a beep and the blue steering wheel icon on the dash (which indicates when LKA is active) went out. That lasted only about five seconds and the system came back on by itself.
I had no real issues with the system and found it worked reliably. I was a driver myself, and I know drivers will take liberties with the hands-off capabilities. I could see them diving into the bunk to throw a sandwich into the microwave, letting the truck continue navigating. Narayanan stressed during our post-ride debriefing that drivers using the systems will require a fair bit of training and orientation — which I also happen to know isn’t some fleets’ strongest suit. I can only hope that fleets investing in such assistance systems supply the necessary training to get drivers to fully understand that LKA is an assist feature, not a self-driving feature — unlike some of those unfortunate Tesla owners who took the Autopilot moniker a little too seriously.
Since this iteration of autonomy is billed as Level 2, it’s intended only as an assistive system. It’s not designated as Level 4, in which case it would be fully capable of self-control with no driver input. This technology is obviously part of the pathway to Level 4, but it’s not there yet.
I worry that drivers might become complacent with this system, considering its apparent competence, and may, at just the wrong moment, fail to intervene before the truck does something it shouldn’t.