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Understanding Vehicle Motion

Brake Testing with Dynamics Duo

Accurate entry speed, clean deceleration traces and repeatable MFDD results so braking performance meets regulatory requirements every time.

100 Hz output rate
±1.8 cm braking accuracy
0.1 km/h RMS Velocity accuracy
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THE CHALLENGE

One weak measurement invalidates the run

Brake testing has no margin for measurement error. Speed, timing, deceleration and distance all need to be accurate, aligned and repeatable – every run, every time.

01

Accurate speed measurement is the foundation

A brake test result stands or falls on the accuracy of the speed measurement. If the vehicle speed at the start of braking is wrong – even by a fraction – the stopping distance and MFDD calculations are compromised from the outset.

02

Trigger timing errors corrupt the result

MFDD and stopping distance calculations depend on knowing exactly when braking started. Any misalignment between the speed signal, deceleration trace and brake event shifts the entire measurement window and undermines the result.

03

Unreliable speed and distance data affects MFDD

MFDD is calculated from speed and distance data. If the speed signal is noisy or the distance measurement drifts, the calculated deceleration figure becomes unreliable and difficult to defend under repeated testing conditions.

04

Run-to-run variation that questions the measurement

When repeated runs produce different results under identical conditions, it is unclear whether vehicle behaviour changed or the measurement did. Without a stable, low-drift reference, variation between runs is hard to explain – whether for regulatory submission or internal development sign-off.

THE SYSTEM

Two instruments. One coherent measurement.

VBOX 4 provides high-accuracy speed, distance and deceleration. IMU05 adds low-noise inertial data referenced to the vehicle's centre of gravity. Together they give you a clean, aligned measurement of braking from trigger to standstill.

VBOX 4
GNSS Data Logger

VBOX 4

100 Hz GNSS measurement engine with dual-antenna heading, CAN data logging and real-time output. The foundation for speed, position and path measurement.

  • GNSS update rate 100 Hz
  • Position accuracy (standalone)H: 1.2 m; V: 1.8 m
  • Velocity accuracy 0.1 km/h RMS
  • CAN ports 2 × CAN + 2 x CAN FD
  • RTK accuracy (optional) V: 10 mm + 0.8 ppm·BL; H: 5 mm + 0.5 ppm·BL
 IMU05
Inertial Measurement Unit

IMU05

Low-noise 6-axis inertial measurement unit. Mounted at a convenient location on the vehicle; lever-arm compensation translates all measurements to the centre of gravity for analysis.

  • Gyro range ±450°/s
  • Gyro bias stability ±1.2°/h
  • Angle random walk 0.08°/√h
  • Accel range ±4 g
  • Accel bias stability 14 µg

WHY DYNAMICS DUO

Four things engineers need. All resolved in one setup.

01

Accurate speed and distance, every run

A brake test result depends entirely on knowing the vehicle's speed at the trigger activation and the distance from there to standstill. Both need to be accurate and traceable.

  • Velocity accuracy of 0.1 km/h RMS for reliable entry speed validation
  • Brake distance accuracy to ±1.8 cm for defensible stopping distance results
  • Speed referenced to the vehicle – not affected by wheel lock or slip
02

Clean deceleration data for reliable MFDD

MFDD is calculated from speed and distance. The quality of those measurements directly determines whether the result is repeatable and defensible – run after run.

  • Low-noise speed measurement unaffected by wheel lock or slip
  • Brake distance accuracy to ±1.8 cm for traceable MFDD results
  • Low-noise Acceleration trace confirms the deceleration profile matches the calculated MFDD
  • IMU bias stability ensures consistent results across a full test day
03

Precise event timing and signal alignment

Understanding a brake event fully means capturing driver input, vehicle response and system behaviour on the same time base – so cause and effect are always clear.

  • Speed, Acceleration and CAN signals merged on a single time base in the VBOX 4
  • Wheel speeds and ABS activity captured via vehicle CAN
  • Optional brake trigger input marks the exact moment braking begins
  • Optional pedal force sensor records driver input alongside vehicle response
04

One setup from development to sign-off

The same Dynamics Duo installation covers early development work and final regulatory submission – reducing setup variation and keeping results comparable across the programme.

  • ISOFIX mount for fast, secure installation across vehicle variants
  • Consistent CG-referenced measurement regardless of vehicle configuration
  • Compatible with UNECE R13-H, FMVSS 135 and ISO 21994 test requirements
  • Real-time pass/fail feedback reduces wasted runs on track

REGULATORY & INDUSTRY STANDARDS

Standards and test frameworks supported

Accurate speed, distance and deceleration data that meets the requirements of every major braking standard.

Standard Test type Measurement challenge How Dynamics Duo helps
UNECE R13-HPassenger Car Braking (Global) Stopping distance, MFDD, fade and recovery tests Accurate entry speed validation; clean Ax trace for MFDD calculation; precise distance measurement 0.1 km/h velocity accuracy and ±1.8 cm brake distance accuracy — speed and distance traceable to a single aligned reference
UNECE R13Heavy Vehicle Braking (Global) Stopping distance and deceleration — trucks, buses and trailers Consistent deceleration measurement across multiple axles and vehicle configurations; stable reference across vehicle changes CG-referenced longitudinal acceleration unaffected by vehicle configuration; consistent ISOFIX installation across variants
FMVSS 135Light Vehicle Brake Systems (US) Stopping distance, thermal fade, partial failure and parking brake tests Entry speed compliance within defined window; stopping distance measurement across multiple test conditions Real-time speed display confirms entry window compliance; ±1.8 cm distance accuracy across cold, hot and recovery stops
ISO 21994Passenger Car ABS Stopping Distance Straight-line ABS braking — open-loop test method Accurate stopping distance on surfaces where ABS activates; speed at ABS engagement; run-to-run consistency GNSS-based speed unaffected by wheel lock; distance resolution of 1 cm; low-noise Ax trace captures ABS modulation clearly
ECE R139Brake Assist Systems Category B BAS performance validation Precise pedal application timing and deceleration response must be captured on the same time base Pedal force (optional), speed and Ax time-aligned on a single reference — BAS activation and vehicle response clearly separated
SAE J2909Light Vehicle Dry Stopping Distance Dry surface stopping distance — trigger brake stops Consistent entry speed and trigger alignment across back-to-back runs on varying surface conditions Stable GNSS speed reference and optional brake trigger input provide repeatable, traceable stopping distance results
UNECE R13-HPassenger Car Braking (Global)
Test type
Stopping distance, MFDD, fade and recovery tests
Challenge
Accurate entry speed validation; clean Ax trace for MFDD calculation; precise distance measurement
How Dynamics Duo helps
0.1 km/h velocity accuracy and ±1.8 cm brake distance accuracy — speed and distance traceable to a single aligned reference
UNECE R13Heavy Vehicle Braking (Global)
Test type
Stopping distance and deceleration — trucks, buses and trailers
Challenge
Consistent deceleration measurement across multiple axles and vehicle configurations; stable reference across vehicle changes
How Dynamics Duo helps
CG-referenced longitudinal acceleration unaffected by vehicle configuration; consistent ISOFIX installation across variants
FMVSS 135Light Vehicle Brake Systems (US)
Test type
Stopping distance, thermal fade, partial failure and parking brake tests
Challenge
Entry speed compliance within defined window; stopping distance measurement across multiple test conditions
How Dynamics Duo helps
Real-time speed display confirms entry window compliance; ±1.8 cm distance accuracy across cold, hot and recovery stops
ISO 21994Passenger Car ABS Stopping Distance
Test type
Straight-line ABS braking - open-loop test method
Challenge
Accurate stopping distance on surfaces where ABS activates; speed at ABS engagement; run-to-run consistency
How Dynamics Duo helps
GNSS-based speed unaffected by wheel lock; distance resolution of 1 cm; low-noise Ax trace captures ABS modulation clearly
ECE R139Brake Assist Systems
Test type
Category B BAS performance validation
Challenge
Precise pedal application timing and deceleration response must be captured on the same time base
How Dynamics Duo helps
Pedal force (optional), speed and Ax time-aligned on a single reference - BAS activation and vehicle response clearly separated
SAE J2909Light Vehicle Dry Stopping Distance
Test type
Dry surface stopping distance — trigger brake stops
Challenge
Consistent entry speed and trigger alignment across back-to-back runs on varying surface conditions
How Dynamics Duo helps
Stable GNSS speed reference and optional brake trigger input provide repeatable, traceable stopping distance results

WHAT YOU CAN MEASURE

Objective, reproducible parameters for brake testing

The parameters below are direct outputs of the VBOX 4 + IMU05 combination unless noted. All are logged, time-aligned and available for real-time display and post-test analysis.

Speed & distance

  • Vehicle speed (GNSS-referenced)
  • Speed at trigger activation
  • Stopping distance
  • Distance accuracy to 1.8 cm

Speed is unaffected by wheel lock or slip — GNSS-based measurement reflects true vehicle motion.

Deceleration & MFDD

  • Longitudinal acceleration (Ax) at the CG
  • Mean Fully Developed Deceleration (MFDD)
  • Time to stop
  • Deceleration profile throughout the event

Brake event & timing

  • Brake trigger timing (optional input)
  • Pedal force (optional sensor)
  • ABS activation and wheel speeds (via CAN)
  • Brake pressure and channel status (via CAN)

Vehicle behaviour under braking

  • Pitch angle during deceleration
  • Yaw rate and lateral acceleration
  • Vehicle path and trajectory
  • Left vs right deceleration comparison (split-µ)

Yaw and lateral data are available for split-µ and stability analysis — see the ESC & Handling page for full dynamics testing capability.

SOFTWARE & ANALYSIS

VBOX Test Suite – from trackside display to post-test analysis

VBOX Test Suite supports your entire test workflow – from live track-side monitoring through to regulatory submission – all within a single platform. Engineers can compare runs, overlay channels from identical test conditions, and export to downstream tools without conversion.

  • Real-time entry speed monitoring with pass/fail window validation
  • Deceleration trace overlay for run-to-run MFDD comparison
  • Multi-run overlay with channel alignment – compare back-to-back or vehicle-to-vehicle
  • Customisable workspace combining charts, maps, and synchronised HD video
  • Automated report generation for regulatory submissions

Data export formats

All VBOX data can be exported for use in other analysis tools such as MATLAB and Python.

.vbbNative VBOX format
.csv Excel & Python compatible
.matMATLAB / Python compatible
.txtTab-delimited text

VBOX CAN output is available for real-time integration with external data acquisition systems.

Ready to discuss your brake testing programme?

Our engineers understand the demands of regulatory brake testing. Contact us to discuss your specific test requirements, vehicle types and preferred standards.

Speak to a VBOX engineer