It's funny how you keep talking about this like the police are A) capable of seeing whether or not your vehicle is on Gridguide and B) constantly looking for vehicles that aren't on Gridguide.
It's not a matter of being on the lookout. It's noticing that the vehicle there can physically be seen, yet it has no corresponding icon in AR. Remember, normal people are in AR every waking second. Traffic cops are absolutely included. So a car with no matrix presence is almost as obvious as a car running without lights on in the dark. If a cop DOES see the car, he immediately knows something is very wrong with how it's operating (assuming, of course, that driving on gridlink is locally mandated).
If the team mage casts Improved Invisibility on your car, yet you remain on Gridguide, are you being a menace to traffic? Hells to the frag yes you are. Being physically invisible but visible on the Matrix is just the inverse of being physically visible but invisible on the Matrix.
In any event, you're severely underestimating how important sensors are.
No, I'm disagreeing that they're relevant to what I'm saying about being cut off from the Matrix is being a menace to traffic that's relying on Gridguide. Lemme try one more time:
Yes, I agree that sensors should pick up the jaywalker or the box that fell out of the back of the truck. That's not the point. The point is sensors, like head/brake lights, are SUPPOSED to be in working order but aren't always. Yes, the car that hit you because it couldn't see you and couldn't passively detect you because you're not on GridLink will also be ticketed for having faulty sensors. But even then, the collision wouldn't have happened if you just were on Gridguide/the Matrix. THAT's why in-universe laws will often/usually/sometimes mandate Gridguide use.
What's more: having working sensors still won't always prevent a collision with a vehicle that's refusing to use Gridguide.
Consider the example I cited. A driver tells gridguide "I'm gonna flip a Yooie here." Gridguide moves the nearby cars just enough to accommodate that maneuver without a collision. Oops, except it doesn't warn you or coordinate with you, since you're not on Gridguide. A car suddenly pulls right in front of you without warning. Crunch. Riggers might get away with dodging that collision, sure. But then again maybe not. And it's quite easy to imagine Gridlink forcing an offline driver into a crash test that mathematically can't be succeeded upon without a rigger's advantages.
It doesn't have to be someone making a sudden U turn in front of you. You could just simply be coming up on a 4 way intersection. Stopsigns and red lights are a thing of the past in many intersections simply because Gridguide exists. The cars detect each other's approach on the intersection despite buildings blocking LOS/preventing sensor acquisition, and Gridguide tweaks their speeds to time their passage through the intersection, allowing both to breeze thru without having dramatically change speed or stop. But if you're going thru and gridguide can't account for you, you can just appear in front of a car with perfectly good sensors and it still doesn't have time to not T-Bone you.
And of course,
again, sensors can be faulty. If sensors alone could be relied upon to prevent collisions, then safe driving practices would also be enough to prevent collisions and noone would ever be pulled over for broken brake lights.