Steady Crawl

Lexus’ new Crawl Control system aims high.

For much of the year, the final road to my favorite mountain getaway is a smoothly paved ribbon that rises steeply through a narrow alpine valley. By spring, however, the preceding months of temperature stress, snow-moving equipment, and water runoff leave the route a cracked, potholed mess before summer crews arrive once again to iron out the damage.

For those who drive this route each spring, picking our way over the unavoidable dips, holes, and bumps—an accelerator punch here, a brake tap there—takes some serious, white-knuckle concentration. Fortunately, Lexus engineers understand that people like me will push our cars up roads like this, and sometimes beyond, to explore remote trails, pursue hungry lake trout, photograph wildlife, or, in my case, enjoy the season’s warm-weather skiing. I know this because Lexus recently unveiled its new Crawl Control[1] technology in the 2008 LX 570.

One way to understand Crawl Control is to look at it as a sort of low-speed cruise control for ascending rugged terrain and slippery surfaces. When activated at slow speeds, Crawl Control allows the driver to take the foot off the pedals and just steer while the vehicle smoothly climbs its way up difficult ground.

However, the system is much more innovative than a typical cruise control function. Unlike normal highway conditions, bumpy or slippery terrain requires a continuous balance of braking and throttle adjustments to avoid slipping or getting stuck. For example, the wrong speed (too fast or too slow), in the wrong spot or at the wrong time, can lead to wheels spinning out and a loss of traction.

This is where Crawl Control comes in. By monitoring each tire’s condition as the LX 570 negotiates extreme terrain, the system can detect too much acceleration, or not enough, for the ground situation beneath the wheels. It then applies an appropriate mix of braking, engine power, and torque adjustments to help keep the wheels rolling at the optimum speeds to minimize slippage.

The result is a confident, steady, automated climb, and all you have to do is steer, although you’re always 100 percent in control: Without deactivating the system, the driver can at any time reduce speed by braking, or increase speed via a speed-selector switch.

In fact, the system works so well that it will move the LX up reasonably navigable boulder-strewn routes; it even works in conjunction with the LX 570’s Active Height Control (X-AHC) system and Adaptive Variable Suspension (AVS), which allow the vehicle body to be raised about three inches, as needed, to avoid bottoming out over particularly rocky ground.