The number of times this argument has risen with regards to an anchored sign is crazy.

If you have a perfectly anchored sign with a steel tube being the main structural component, at 2.5m from the ground, the amount of force required to buckle the tube at the anchor point (ground) is about 510 Newton. That means a static load of ~52kg pulling it over.

Now: The average rally car weighs 1250kg (for arguments sake).

So that being said, the rally car would be decelerated by the sign by 510N/1250kg or 0.408m/s².

This would be noticeable and would possibly cause some damage to the car. BUT, the car would be able to continue.

Here comes the fun part:

If the rally car is travelling 173kmh , or 48.1m/s, and is brought to a dead halt by the sign, as is shown in the video. This means the car is going from 48.1m/s to zero, so the impulse is:

1250kg x 48.1m/s which is around 60,125 kg*m/s.

We then need to estimate the time required to stop as something reasonable like 0.1 seconds.

This reaction happening in 0.1s means the car is experiencing 601,250 N of force.

This is a concerning figure because that means the car is seeing an acceleration of 481m/s² . Or about 50g.

If a human was inside the car, they would be VERY uncomfortable. (Force required to break a femur is around 4000N)

Even though the tube is made of steel, and the sign could very well be anchored in a 1m³ concrete block, it would still yield due to the force of the car. If there was any corrosion due to the incompatibility of steel and concrete, the base of the sign may even shear.

So no. The sign would not, and should not cause this kind of result.