Smart phone GPS Illegal?

A recent article by the News Mail stated that Smart phone GPSs are illegal. The headline certainly caught my eye, and the picture of a policeman holding up an iPhone sporting a GPS app certainly nailed the point home. Wha ??

I rang the police department later that day for clarification. If using the GPS features of an iPhone are classed as using a phone, what about using other features such as, say, listening to music? If this point stood, you may as well fine everyone with an iPhone. Fortunately the clarification made the point clear: OPERATING a phone is illegal. Using the phone in hands free mode for any feature is acceptable.

GG News-Mail. I think that distinction is critical to the balance of the article.

MOTORISTS are being warned that smart phones such as the iPhone will cost them a $300 fine if they are used as a navigational device while on the road.

Uhh, I would expect the people who have shelled out ~$50 for GPS maps have also shelled out for an in-car cradle to make it easy to use, placing it in exactly the same legislative position as an ordinary GPS unit.

By the way, I don't see any laws against using a laptop while driving. Maybe the legislation surrounding phones needs to cover distractions in general caused by in-car devices?

Accelerating to 100

I made a guesstimate in the post about slow drivers regarding the time it takes to accelerate back up to 100 from a stop to join back in the traffic. The guesstimate of 10 seconds was based off my own evaluation of how far away a car would be before I'd decide to pull out from a standing start, and then relating that distance to the time based method used for shadowing cars. I'd guessed that about 6 seconds would be the limit for me, so about 10 seconds would be comfortable for most people.

10 seconds sounds a short amount though. Most cars wouldn't accelerate to 100 in 10 seconds comfortably, but while you're accelerating away you are also putting distance between you and the car behind. So how much time is gained by the increase in speed? Some quick math:

100km/h = 27.2m/s (since we're going to be working in seconds)
Assuming constant acceleration to reach 100km/h in 10 seconds, you'd get a graph like this:


The actual distance travelled is the area under the graph, which, as it's a right triangle is simply length*breadth/2.
= 27.7m/s*10s/2
= 138.8m

The approaching car has another 138 metres to cover, which it can do in distance/speed.
= 138.8m / 27.7m/s
= 5s

5 seconds, or exactly half the time. That's what I thought immediately, but a couple of math dead-ends while watching the footy had me looking up all sorts of parabolic complexities.

So with 1/2 the time given back to the merging driver, that would mean my guess of a 6 second gap for merging would mean going from 0-100 in 12 seconds. That's achievable even in my corolla, but doubling the 10 second gap to 20 seconds for 0-100 certainly sounds achievable by the majority of the population. Can't seem to find any average acceleration for general driving conditions tho :/

So that's for merging, the same goes for rejoining from pulling over. The time lost compared to continuing on at the driver's original speed is the time taken to get to the original speed minus the time it would have taken to cover the distance used to get to that speed. So, the same result. 1/2 the time. 20 seconds to get back up to speed means you have only lost 10 seconds. This also goes for decelerating, so the figures of 10 seconds for deceleration, 10 seconds for letting them pass, and 10 seconds to rejoin would seem highly achievable.

Let them Pass

Mum & Dad came down last night for the Maundy Thursday service and mentioned the huge amount of traffic on the road over breakfast. Why is it that when there's lots of people on the road you always seem to get stuck in a massive lineup behind someone doing 80 on the highway? I lamented too that it's actually inconsiderate of the slow drivers to not pull over and let them pass. This builds on the 2nd of 2 driving principles: Be aware, Be Courteous.

It suddenly struck me that you should be able to calculate WHEN you should pull over depending on the speed and number of people following. If you are trying to maximize the trip for everyone, then it's simply when the cost of pulling over is less than the loss of time by everyone behind.

First, the cost of pulling over. I'd guess that 30 seconds would be a reasonable figure. That gives 10 seconds lost while braking, 10 seconds to let the traffic past, and 10 seconds to get back up to speed. I reckon I could get under way and get up to speed with a car 6 seconds away, so 10 should be comfortable.

Second, the cost of the people behind. If the person in front was doing 90km/h and the people behind were travelling at 100km/h, the difference is 10km/h of lost 'time'. The ratio of current speed to desired speed difference is therefore 90km/h : 10km/h , or 9:1. So a 30 second loss in 'time' through difference in speeds therefore translates to 4 & 1/2 minutes of driving time by the lead driver. At 90km/h that would translate to almost 7kms of road.

That seems reasonable. ~5minutes following someone over 7kms would have at least a couple of opportunities to pass. If someone was stuck behind me for that long I'd consider looking for ways to let them pass.

Now lets look at someone doing 80km/h with 4 cars behind them wanting to go 100km/h.

80km/h : 20km/h * 5
8 : 10
24secs : 30secs

~20 seconds before you are inconveniencing the people behind you more than the 30 second effort to get off the road. In other words, you're an inconsiderate driver if you don't pull over at the next opportunity.

Keep in mind this has nothing to do with the amount of passing lanes, the amount of pull-in spots, whether you're going 80 and the guy behind only wants to do 90, it's purely about maximizing the journey of all participants. It's about being considerate of all travellers, not just yourself.