In g
Accelerometer style
- Setting
- 0.449 g
- In m/s²
- 4.40 m/s²
- In km/h per s
- 15.8 km/h per s
Driver safety · Free calculator
Harsh-event threshold translator and stopping-distance check
One vendor sets harsh braking in g, another in m/s², another in km/h per second. Enter any one, get the rest, and see what the threshold means in meters on the road.
How is the threshold written?
A setting is written as a value, such as 0.45 g, or as a time, such as 60 km/h in 3.95 s.
Chooses which published defaults your value is compared with.
Example: 4.4. Read the unit on the settings screen before you type.
0.45 g is not 0.45 m/s². Pick the unit your setting uses.
s
Seconds to change the speed by the amount below. Example: 3.95.
km/h
60 km/h in 3.95 s is 0.43 g.
× g
The most braking or cornering the tires can give, as a fraction of g. 0.7 is a typical dry-road value. Use less for wet roads or loaded heavy vehicles.
Typical value. Replace with your own road and tire data.
How this is calculated
m/s² = g × 9.80665 = mg × 0.00980665 = km/h per s / 3.6
km/h per s = m/s² × 3.6
time to change speed by dv = (dv / 3.6) / a
Deceleration to use
Your threshold shows how far a driver goes when braking exactly at the setting. Road grip shows the shortest stop the road allows.
m/s²
Example: 6. Used only for the stopping distance.
km/h
Speed when the driver sees the hazard. Example: 80.
s
From seeing the hazard to pressing the brake. 1.5 s is a typical design value.
Typical values. Replace with your own driver and road data.
How this is calculated
reaction distance = v × t
braking distance = v² / (2a)
total = v × t + v² / (2a)
time to stop = t + v / a
(v in m/s: km/h / 3.6)
km/h
Example: 90.
m
Distance when the driver first sees it. Example: 60.
s
1.5 s is a typical design value.
The check uses the threshold and the grip factor from the Convert tab.
Typical values. Replace with your own driver and road data.
How this is calculated
braking needed = v² / (2 (D - v × t))
if v × t is at least D: no room to brake
impact speed = sqrt(v² - 2 × a_max × (D - v × t))
a_max = grip factor × 9.80665
Threshold in every unitExact conversions · typical assumptions
Stopping distanceExact conversions · typical assumptions
Hazard gapExact conversions · typical assumptions
Take this to your commissioning test
Report with the conversions, the comparison and the stopping table.
Threshold report
Get the threshold sheet for your configuration file
- Your threshold in g, m/s², mg and km/h per second
- Comparison with published defaults for the same event
- Stopping distance table at your reaction time
- Hazard-gap table against your threshold and road grip
- Method and sources
A quick conversion table
| g | m/s² | km/h per s | 60 km/h in (s) |
|---|---|---|---|
| 0.10g | 0.98 | 3.5 | 17.0 |
| 0.20g | 1.96 | 7.1 | 8.5 |
| 0.30g | 2.94 | 10.6 | 5.7 |
| 0.40g | 3.92 | 14.1 | 4.2 |
| 0.50g | 4.90 | 17.7 | 3.4 |
| 0.60g | 5.88 | 21.2 | 2.8 |
| 0.80g | 7.85 | 28.2 | 2.1 |
| 1.00g | 9.81 | 35.3 | 1.7 |
Exact conversions at constant acceleration. Only the thresholds you pick are assumptions.
Three checks before you save a setting
- Read the unit label. g, m/s² and km/h per second differ by a factor of 9.8 or 3.6.
- Compare with the event type you set, not with another event.
- Test on one vehicle and count events before you send the setting to the fleet.
One threshold
The same braking, written three ways
A settings screen may show any of these. They describe the same braking.
In m/s²
SI style
- Setting
- 4.40 m/s²
- In g
- 0.449 g
- In km/h per s
- 15.8 km/h per s
As a time
Driver style
- Setting
- 60 km/h in 3.79 s
- In m/s²
- 4.40 m/s²
- In g
- 0.449 g
References
Where two published settings start
Telematics vendors publish their default harsh-event settings. They are a starting point for a trial, not a rule. Re-read on 2026-11-03.
| Event | Vendor A | Vendor B |
|---|---|---|
| Harsh acceleration | 4.4m/s² (0.449 g)published | 0.43g (4.22 m/s²)published |
| Harsh braking | 4.4m/s² (0.449 g)published | 0.61g (5.98 m/s²)published |
| Harsh cornering | 5.5m/s² (0.561 g)published | 0.47g (4.61 m/s²)published |
| Test levels (vendor A) | 3.0 / 3.5m/s²published | |
Published values of other vendors, shown for comparison. Values re-read on the vendor pages on 2026-11-03. No standard sets these thresholds. Vendor B states the least sensitive setting of its default rule. They are not Tracom settings.
Sources: Vendor A support page · Vendor B article
What does the harsh-event threshold translator do?
Harsh-driving thresholds are written in different units from one settings screen to the next. This tool converts one value to all the others. It then answers two questions an installer is asked on site: where does this threshold sit against published defaults, and what does it mean in meters on the road?
The Convert tab gives the threshold in every unit and compares it with published references. The Stopping distance tab shows how far a vehicle travels before it stops. The Hazard gap tab asks whether a driver who sees a hazard ahead can stop in time, and whether doing so would log an event.
Why do the units differ?
- g is a multiple of standard gravity. 1 g is 9.80665 m/s².
- m/s² is the SI unit. Many device settings use it.
- km/h per second is the one drivers feel: how much speed you gain or lose every second.
- A time, such as 60 km/h in 3.95 s, is the same acceleration written as a stopwatch reading.
Inputs you need
| Input | Where to find it | Tip |
|---|---|---|
| Threshold value and unit | Device configuration or platform rule | Copy the unit label exactly. Never assume it. |
| Event type | The rule name | Braking, acceleration and cornering have different published references. |
| Road grip factor | Your roads, tires and loads | 0.7 is typical for dry asphalt. Use less for wet roads or loaded heavy vehicles. |
| Speed and reaction time | Trip data and your driver standards | 1.5 s is a typical design value. Edit it. |
| Hazard distance | A site survey or a recorded event | Use the distance at the moment the driver first sees the hazard. |
How it is calculated
Units
g = a / 9.80665
mg = g × 1,000
km/h per s = a × 3.6
time to change speed by dv = (dv / 3.6) / a
1 g = 9.80665 m/s² is standard gravity, defined by the CGPM in 1901 and listed in ISO 80000-3.
Stopping distance
total = v × t + v² / (2a)
time to stop = t + v / a
Hazard gap
braking needed = v² / (2 (D - v × t))
impact speed = sqrt(v² - 2 × a_max × (D - v × t))
a_max = grip factor × 9.80665
All of it is constant-acceleration kinematics. The grip factor, the reaction time and the published references are the only assumptions, and you can edit all three.
Worked example: a 4.4 m/s² braking threshold
- Units: 4.4 m/s² is 0.449 g, 449 mg and 15.84 km/h per second. A 60 km/h change takes 3.79 s.
- Comparison: published braking defaults run from 4.40 to 5.98 m/s². The value is inside that range and about 64% of the grip limit (6.86 m/s² at a factor of 0.7).
- Stopping distance: from 80 km/h with 1.5 s to react, the vehicle travels 33.3 m before braking and 56.1 m while braking: 89.5 m in 6.55 s. A shorter stop needs harder braking and logs an event.
- Hazard gap: at 90 km/h with a hazard 60 m ahead, stopping needs 13.9 m/s² (1.42 g). That is beyond road grip, so the vehicle reaches the hazard at about 64 km/h.
Reading your results
- Inside the published range means other vendors start in the same place. It does not mean the value is right for your fleet.
- More sensitive logs more events. That helps a trial and floods a review team.
- Above road grip almost always means a unit mistake.
- Event logged in the hazard table means a correct reaction still triggers the rule. Change the speed, the following distance or the threshold, not the driver.
Common mistakes
- Typing g as m/s². 0.45 entered as m/s² is a tenth of the intended braking.
- Mixing mg and g. 450 mg is 0.45 g, not 450 g.
- Copying a car threshold to a loaded truck. A heavy vehicle cannot brake as hard, so the rule may never fire.
- Comparing event counts across device types. Each device reads and filters acceleration its own way.
Assumptions and limits
The stopping figures assume constant deceleration on a level road. Real stopping depends on brakes, load, tires, slope and surface. Use them as a sanity check, not as a braking test. Published references come from other vendors, were re-read on 2026-11-03, and are not recommendations. This page does not state the accelerometer range, resolution or default thresholds of any Tracom device. Take them from the device documentation. The right threshold for your fleet comes from a trial: start sensitive on a few vehicles, count events, and raise the value until the list is short enough to review.
Related Tracom solution
Set the threshold once, test it, then apply it to the fleet
Tracom publishes Driver Behavior Monitoring with Voice Alerts, Advanced Configuration Files and Over-the-Air Update among its features. Ask which event settings your device profile exposes, in which unit, then check them here.
- Driver behavior monitoring with voice alerts. Ask how the voice alert is tied to the events you configure.
- Advanced configuration files. Ask how one tested set of values reaches many vehicles.
- Over-the-air updates. Ask how a changed setting follows without a visit.
- SCMS portal. Manages device settings and configuration files in one place.
What is the difference between g and m/s²?
g is a multiple of standard gravity, 9.80665 m/s². So 0.45 g is 4.41 m/s². It is the same acceleration in a different unit. Always check which one the setting asks for.
How do I convert km/h per second to g?
Divide by 3.6 to get m/s², then divide by 9.80665. For example, 15.84 km/h per second is 4.4 m/s² and 0.449 g.
Which threshold should I use for a truck or a bus?
There is no single right number. Heavy and loaded vehicles cannot brake as hard as a car, so a car-style value may never fire. Start sensitive on a few vehicles, count events per 100 km for a week, and raise the value until the list is short enough to review.
How accurate is the stopping distance?
It is a sanity check. It assumes constant deceleration on a level road and your reaction time. Brakes, load, tires, slope and surface change the real distance.
Why does the same threshold log a different number of events on different devices?
Devices read acceleration from different sources and filter it differently. A value taken from GPS speed is an average over the reporting interval, while an accelerometer sees shorter peaks. The mounting angle matters too. Compare counts only on the same device type, with a test drive.
Does Tracom state its device thresholds here?
No. This page does not state the accelerometer range, resolution or default thresholds of any Tracom device. Take them from the device documentation. The published defaults in this tool belong to other vendors, are shown for comparison, and are not a recommendation.
Plan the trial
Test your thresholds with Tracom before you roll them out
Tell us the vehicle types and the events you want to catch. We will explain how Tracom devices expose those settings.
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