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Can you answer this question before my traffic court at 9 am?
June 10, 2014 4:41 AM   Subscribe

I'm due in traffic court at 9 am. Help me use math to prove I didn't do it.

Long story short: officer says I went from 0 mph to 29 mph within a distance of about 200 feet. There is no way I got my little Honda Fit up to that speed within that distance.

Is there any science: simple math about acceleration; or somehow using the Honda Fit's 0 to 60 speeds (2007 Honda Fit Sport 0-60 mph 8.9 Quarter mile 16.6) to use SCIENCE! to help me be persuasive that I didn't do this.
posted by anastasiav to Law & Government (15 answers total) 3 users marked this as a favorite
 
Here.
posted by hal_c_on at 4:57 AM on June 10 [1 favorite]


If we assume constant acceleration (which is probably not what actually happened, but let's go with it for now) then the distance travelled is given by:

d = 0.5 * a * t^2

Assuming your acceleration is constant, acceleration is given by:

a = Δv / t

Combining those equations:

d = 0.5*Δv*t

Solving for time:

t = 2*d/Δv

Using the numbers in your situation, t = 9.4 s, so that would be 0-29mph in 9.4 s.

That's equivalent to 0-60mph in 19.5 s, which, sorry, is well within the capabilities of the Honda Fit.

Again, note that this assumes constant acceleration. It's possible that the details of engine performance could suggest that your acceleration profile must have been lower, but I don't have the expertise to say so.
posted by Salvor Hardin at 5:08 AM on June 10 [9 favorites]


Flat-out, I get about 57 feet, given Car and Driver's test sheet and some calculus, assuming constant acceleration (which is close-enough in first gear in a real Fit). The actual distance traveled might be a bit longer, but it's certainly possible to get up to 30mph in well under 200 feet in a Fit (I'm sure I did it this morning, in fact). 200 feet is probably a bit longer than you think.
posted by uncleozzy at 5:14 AM on June 10 [2 favorites]


Be prepared for the possibility that the traffic court isn't going to be interested in hearing your math. Can you come up with a non-math explanation as a backup?
posted by J. Wilson at 5:17 AM on June 10


There is no explanation. I wasn't going that fast - pulled out of the driveway into moderate traffic. I would have had to been driving like a rally car driver to get up to speed that fast (which I wasn't -- I was still in first gear when he pulled me over).
posted by anastasiav at 5:26 AM on June 10


What was the speed limit, 25? 29 in a 25 zone doesn't seem like a ticketable offense, especially if you're merging into traffic and trying to go with the flow. I'd hang your appeal on that.
posted by beagle at 5:30 AM on June 10 [1 favorite]


15. It's a $137 ticket.
posted by anastasiav at 5:38 AM on June 10


Say exactly what you already said here. "I wasn't going that fast - pulled out of the driveway into moderate traffic." Even if they asked if it was possible, you say NO.
posted by Yellow at 5:43 AM on June 10 [3 favorites]


Appeal to common sense, and maybe at least they will reduce the fine. "I would not go twice the speed of traffic on the road, in a driveway, to merge into said traffic."
posted by mikepop at 5:56 AM on June 10 [7 favorites]


Agreeing with others that basic common sense trumps complicated math in court, especially when the math doesn't 100% CYA.
posted by mkultra at 6:18 AM on June 10 [6 favorites]


Sounds like he may have been trying to give you a break. At 30 the charge may have been a more serious "reckless driving" or some such , so, as you may have actually been speeding, he just made it out for a speed that would only mean a ticket.
posted by The 10th Regiment of Foot at 7:17 AM on June 10


Upon a little research I see that 15 MPH is the limit that puts a Maine driver in a higher penalty level known as "Driving to Endanger" which carries a $575 penalty or 1-6 months of license suspension. Source.
posted by The 10th Regiment of Foot at 7:25 AM on June 10


Sounds like he may have been trying to give you a break.

Alternately, it sounds like he was citing her at the highest possible speed before the charge would have increased and she would have gotten a lawyer to fight a reckless driving charge, i.e. reducing the chance she would just pay the ticket and not fight it.
posted by mikepop at 7:33 AM on June 10 [8 favorites]


I know this is too late to help you, but instead of doing the math, I did some practical hands-on experimentation.

I took my manual Fit Sport to a safe location (no traffic, car or pedestrian, 40 mph speed limit) to see how quickly I could gun it to 25-30 mph while in first.

Over a distance of 250 feet, I was able to keep the car in first and reach about 27-28 mph before I shifted. I was a little too close to redlining the engine for my comfort, so I didn't try to push it all the way to 30. My Fit Sport redlines at about 6700 or 6800, and by the time I hit 25, I was already a good 5500 and rising fast.

My little experiment brought me to two conclusions:

1. Unless you redlined your engine, I highly doubt you stayed in first and reached 29 mph in 200 feet. The officer definitely overestimated your speed... or you didn't stay in first if you have an automatic.
2. I also highly doubt that you don't deserve the ticket. Fits are wimpy little cars but they can certainly clear 25 mph in a very short space. I was amazed by how quickly I could jump past 20, much less 30... and if you're going over 20 in a school zone (which I'm assuming your 15 mph zone is, like in most states), tickets will happen.

Sorry about your ticket.
posted by Old Man McKay at 10:35 AM on June 10 [2 favorites]


Thanks, everyone, for your help.

I'd just like to say that going to traffic court is a great way to remind yourself how broken our system is. The process this morning was basically -- have your name called; tell the judge that you'd like a) to plead guilty; b) have a trial immediately; or c) discuss. Most people chose "discuss" -- which means that you 'discuss' your infraction with the officer who cited you in the first place.

My officer was not there. In the old days, that would have meant the charge was dismissed, but now the "representative officer" basically told me I had two choices: wait for as long as it would take them to go back to the station and pull the video of my stop, and then have that evidence entered for "trial" (and I was told several times that might mean I was there "all day" and "a long time") or I could have the infraction "filed" -- I'd pay $75 "costs" and the ticket would be set aside for 6 months. If I didn't have another stop within 6 months it would not go "on my record".

I took the deal, but I feel dirty.

Thanks for all your help, though.
posted by anastasiav at 12:39 PM on June 10 [6 favorites]


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