Speedometer vs. Waze: Which is more accurate?

Map Editors Community Israel - Israel Waze app
1

Iโ€™ve noticed for a long time that the speedometer and Waze donโ€™t show the same speed.
My question is, which one is more accurate?

2

Waze calculates the speed at which you cover the distance from point to point
compared to the car, which translates the rotational speed of the flywheel on the gearbox into driving speed
in my opinion, Wazeโ€™s speed is more reliable

3

In vehicles, the speedometer tends to โ€œlieโ€ upwards intentionally, meaning it shows a speed slightly higher than the actual speed.
In practice, for most vehicles, the error is between 2% and 7% upwards, depending on the model, tires, and speed.
The main reasons for this:

  1. Legal and Regulatory Requirements โ€“ According to international standards (such as in Europe โ€“ the UNECE R39 standard), vehicle manufacturers must ensure that the displayed speed is never lower than the actual speed. The gauge can show up to about 10% + 4 km/h more, but never less. This is intended to prevent a situation where a driver believes they are traveling at, for example, 90 km/h, but is actually traveling at 100 km/h and breaking the law without knowing.

  2. Tire Variance โ€“ Tire diameter affects the calculation. Over time, the tire wears down and the diameter decreases slightly, which increases the calculated speed. Additionally, people replace tires with different (but approved) models, and this changes the reading. The upward deviation takes this into account.

From the European Standard:
Section 5.4:
โ€œThe speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.3.5 above, there shall be the following relationship between the speed displayed (Vโ‚) and the true speed (Vโ‚‚):
0 โ‰ค (Vโ‚ โˆ’ Vโ‚‚) โ‰ค 0.1 Vโ‚‚ + 4 km/hโ€

4

The less air in the tires, the more the gauge deviates to the โ€œ+โ€ :)))

5

I think Waze isnโ€™t completely accurate eitherโ€”does it calculate progress in altitude? Meaning: on a steep climb, Waze will show a lower speed than the actual one. In a plane, there is a special gauge for this: Vertical speed.

6

Definitely not. When I start going up or down steep inclines while the car is on cruise control, the speed on Waze always drops by a few km/h even though the speedometer shows a stable speed, the wheels are the same, and thereโ€™s no slipping on the road.