MAX GRIP Belying its raised ride height, the Ford Focus Active scored even higher than the Mazda 3 at 0.87g
EXPLORING THE OUTER LIMITS OF ADHESION ... AND BEYOND
TO ASSESS each vehicle’s maximum lateral grip, an Oxford RT3200 inertial and GPS measurement system was rigidly installed at the approximate centre of gravity location to measure forward and lateral velocity and lateral acceleration, corrected for roll angle. The test course was a ring of cones 60 metres in diameter laid out on Lang Lang’s concrete skid pad.
Speed was gradually increased until stability control
(ESC) intervention occurred or the vehicle was unable to maintain the circular course. All runs were completed with ESC activated, though the dual cabs were also tested with ESC disengaged due to the systems’ early intervention.
Each vehicle was tested two-up and completed two runs in a clockwise and anti-clockwise direction for a total of four runs.
As one might expect of one of the best-handling small cars available, the Mazda 3 performed well with a maximum reading of 0.83g, the testing notes reading: “Subjectively felt the best of all vehicles due to low centre of gravity and the supportive seat giving more sporty feel. Ultimately limited by ESC intervention”.
Belying its raised ride height, the Ford Focus Active scored even higher at 0.87g, the test notes explaining the Goodyear tyres felt the grippiest but its ultimate potential was again limited by ESC. Once again the Ford Escape defies the SUV reputation by splitting the two hatches with an impressive 0.85g reading, its steering “sharp and precise”.
The CX-8 was the only vehicle not limited by ESC intervention, its front tyres eventually washing wide into understeer at 0.78g. A look at the spec sheet reveals its Toyo Proxes are the same width as the Continentals on the Escape at 225mm, yet they are tasked with controlling almost 400 extra kilograms.
Both dual cabs recorded very similar results, the Ford Ranger having a slight edge with ESC activated at 0.70g to the Mazda BT-50’s 0.68g. The testing notes for both utes describe greater roll, reduced steering response and very conservative ESC calibrations.
Repeating the test with ESC deactivated in the Ranger made very little difference due to roll-over mitigation remaining active and keeping the electronics alive, while relying purely on mechanical grip in the BT-50 increased its reading to 0.74g.
ASSESSING AUTONOMOUS emergency braking systems required a bit more science. Each vehicle was fitted with a GPS speed sensor and an impact trigger on the front bumper and driven at a ‘Guided Soft Target’ (GST) on a constant throttle. The GST is a Ford Fiesta lookalike made up of a number of foam blocks; the speed starts at 10km/h and builds in 5km/h increments to a maximum of 50km/h, which is the speed used by NCAP to evaluate AEB.
The good news is that all vehicles avoided the GST at all speeds up to and including 50km/h, however the execution of the AEB systems varied quite dramatically between manufacturers, as did the distance-to-impact once each vehicle had come to a complete halt. All tests were conducted with the AEB sensitivity set to its middle setting as per NCAP protocols.
Class of the field was the Mazda 3. The closest it ever came to hitting the GST was 1.37m at 10km/h and typically stopped more than two metres short of the target. In fact, the efficacy of the 3’s AEB is such that it easily avoided the GST even when the speed was increased to 55, 60 and 65km/h. The testing notes stated the following: “Very early forward collision warning with minor braking until a last-minute ABS stop – hard, consistent. Stopped furthest away for the target vehicle”.
It was a similar story with the Mazda CX-8. While it cut things closer compared to the 3, getting within 0.58m of an impact at 35km/h, it also stopped short of the target at speeds up to 65km/h. The testing notes read: “Late braking and full ABS stop, stopped with large safety margin each time. Tested an additional point at 65km/h and stopped comfortably”.
The BT-50 performed well, stopping easily at all speeds up to 60km/h, though in the 65km/h test it impacted at 22km/h. Testing notes: “Late warning, firm braking into hard ABS stop, probably the harshest of the lot. Constantly had a ‘Front Camera Unavailable’ warning after every third test, requiring a key cycle to reset. With this fault AEB and lane support systems were unavailable”.
Switching to the Fords, the Escape ST-Line easily avoided the GST at all speeds up to 45km/h, though typically with only around half-a-metre to spare, a result of Ford’s AEB strategy, which we’ll get to shortly. From 50km/h it stopped just 6.5cm (0.065m) short of the target, from 55km/h it impacted at 2.5km/h and from 60km/h 19km/h. Nevertheless, the testing notes were complimentary: “Very smooth braking. The stop felt as if the brake was applied firmly by the driver, not an emergency intervention, [with] no suspension recoil during the stop”.
The Focus Active performed similarly, in general stopping around half-a-metre shy of the target at all speeds up to 50km/h, though from 55km/h it impacted at 8.2km/h and from 60km/h 18.7km/h. Testing notes: “Smooth braking. Not quite as smooth as the Escape but still very good. Hard braking at start before lifting and a solid stop – a standard Ford strategy it seems”.
At speeds up to 50km/h the Ranger likewise stopped well short of the GST, but beyond the NCAP threshold it impacted at 14.1km/h from 55km/h and a hefty 28km/h from 60km/h, scattering the various pieces of the foam Fiesta in all directions.
It’s pleasing that all vehicles stopped safely at all speeds up to and including the 50km/h dictated by NCAP, though credit to Mazda for having an AEB system that works effectively at speeds well beyond that. There is more to the story, however, which can be explained by the testing notes.
“All Ford vehicles applied a noticeable brake pulse together with the Forward Collision Warning to warn the driver of an impending condition. The brakes would then release and reapply for full AEB braking to avoid the target. In a real-world situation, we’d expect the driver to react to the initial warning, apply the brakes and hopefully avoid the target without the need for AEB intervention, especially at higher speeds”.
In contrast, “The Mazda vehicles were able to identify the target vehicle and apply AEB braking as late as possible to avoid the target (single brake application)”.
The execution of the AEB systems varied quite dramatically between manufacturers