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Comment by nsxwolf | Hacker News Reader

If the police are measuring with ultrasonic rangefinders, then cars need them too. How are human drivers supposed to judge that distance?

The article makes the analogy of trying to enforce speed limits without a radar detector. Fine, but cars have speedometers that give the driver the same information. We don't demand drivers just get a feel for how fast they are going.

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I do it by overcompensating so there is no chance I am too close to the cyclist. If there is not enough room (e.g., oncoming traffic) then I wait until there is an opportunity. I can't see cars broadly introducing this technology before we're not the ones driving them.

FWIW, I worked on a "citizen jury" that recommended the adoption of the one-metre passing rule in my state. The default opposition on the jury was "what if there isn't enough room?" Many didn't think to presume that give way rules could apply in this situation. No one raised your point about equivalent technology. I guess the difference is that I am good at estimating one metre but poor at estimating 60km/h.

Hear, hear. There have been times that I'm certain the cyclist I was waiting to pass was annoyed that I wasn't passing in city traffic but the law says three feet so I give them three feet. In the main it's because if I passed with less than three feet and something happened, including the cyclist losing control, I would, of course, be crucified by law enforcement and the cyclist, assuming they survived the incident.

I do the same thing. To me, a cyclist is a "car" in the sense that regardless of their actual road position I treat them like they're taking up the entire lane and look for a window to overtake them.

I guess in my head, I assume that a cyclist could hit a rock at any moment, fall over, and get caught under my tires. So I treat the situation like that is a realistic scenario even if perhaps it is not.

I wish cyclists would cycle more centrally in their lane. Cycling near the curve just results in bad drivers thinking they can ride side by side with a cyclist which they should not be doing...

Exactly. And beyond hitting a rock, they may have to adjust their line to dodge debris that would not trouble a car tyre.

As part of the jury, one member who was a cyclist showed me a first-person video of his commute overlaid with descriptions of why he changed his position when he did - it was very interesting, and the risk of being 'doored' was palpable. I think many drivers would benefit from seeing something like this.

We do ask people to guess whether or not they are committing DWI/DUI though, which is a huge problem in my opinion. Cockeyed.com sums it up better than I can:

http://www.cockeyed.com/science/breathalyzer/breathalyser01....

> Monitoring blood alcohol levels is difficult. Holding people accountable for crossing the .08 limit is like holding them accountable for trespassing once they walk past a particular longitude. The line is invisible. It is possible to determine your longitude, but it is awfully tricky if you don't own a sextant or GPS unit.

> Imagine if cars did not have speedometers, but speeding laws were still enforced with $2,000 police radar guns. It would be really difficult to tell how fast you were going, particularly (as is the case with blood alcohol levels), you had never experienced having your speed tested, nor had any real experience with what a particular speed (for example 55 mph) feels like.

There's two ways to ensure that you aren't inadvertently running afoul of drinking and driving laws: you can either not drink, or wait a large amount of time after drinking before you drive.

Same with passing bicycles - you can give them so much more than three feet that there's no chance that you're within three feet of them, or not pass them until there is that much room.

Three feet is the minimum. The expectation isn't that drivers should try to get as close to three feet without going over.

Should we treat speed limits the same way, so everyone drives around at a crawling pace?

You could do that. But most cars come with a handy dashboard-mounted speed indicator device, often in plain view of the driver - so you could use that to determine your car's speed instead.

You should, uh, read the whole thread, it's an analogy.

The comparison doesn't strike me as a very good one. There are no good, quick, easy ways of measuring how far from a cyclist you will be when you pass them, or your blood alcohol content (which is anyway only a crude proxy for level of intoxication, and besides is commonly measured by alcohol in one's breath, which isn't quite the same thing). That's why people are advised to err on the side of caution.

When it comes to speed, on the other hand, every car comes with a speedometer. Erring on the side of caution would not be a crime (the speed limit is a limit, after all, not a goal...), but it's far less necessary.

It's a pretty crappy analogy.

Would make everybody safer.

What's the problem with using a breathalyzer? Seems like a good investment if you want to drive after drinking often.

France mandated breathalyzer kits in all cars a few years ago, although it has since been suspended[1].

[1] http://www.thelocal.fr/20130124/france-motorists-drivers-sus...

The 3 feet is a minimum. The idea is just to leave a reasonable amount of room. If someone passed a post at speed with only 3 feet of clearance they would be checking to see if their mirror was still there.

There are many laws like that, following too close comes to mind. If in doubt, wait to pass until you're sure you have room.

Following too close is rarely enforced, and it is a big problem. It appears like technology might help mitigate this one, radar-based systems are becoming more standard and several systems are designed to warn when you travel too close for a given speed. Additionally radar based cruise control means that even if you DO travel too close, the faster reaction of the system might avert a collision.

Yep, it's the cause of many accidents. I noticed that Tesla's new cruise control uses radar and adjusts the speed to maintain adequate distance [1]

[1]: http://arstechnica.com/cars/2015/05/review-teslas-new-model-...

As a cyclist I don't mind cars that are only two feet away, or even only one foot if they're not going that much faster than me. It'd be pretty awful to be ticketing people for only being 35" away (especially since riding in a 1" band is not feasible on most streets, so most of them wouldn't even be the car's fault), but on a lot of streets you could be pretty much continuously writing tickets for passing 6" away, and blaming a lack of instruments for that would be like blaming a broken speedometer for going 50 in a 25 zone.

Close distance passing may be more tolerable for experienced and fully competent cyclists, but it's still unnecessarily risky. And the risks are much higher for those with less sure bike handling skills: new and casual riders, and the very young. It's not uncommon to see these kinds of riders wobbling back and forth, "salmoning" their way down the road, obviously lacking good situational awareness.

There are just so many reasons why it's a good idea to give cyclists a wide berth, but perhaps they all come down to this: The extra space provides a more adequate margin for error in the event of unforeseen and emergency circumstances, for both driver and cyclist.

Judging 45 miles per hour is a lot different (and difficult) than knowing how far three feet is.

I think the device is used partly as education, partly as a method for capturing the exact distance. It's less about "how far is three feet?" and more "I have proof you were closer than three feet".

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