Hi Ozb,
Never thought it would be my day to post a speeding/car crash related thing here, but here we are.
See the images for detail: https://imgur.com/a/KVsjhTM
Today I got booked by a cop by radar gun going to the doctor's to get a medical note for work.
I was behind a black sedan and we both turned right from Gillespie Rd onto Station St, a main road which is speed signed for 70km for most of it. We both stopped at a red light right after Mcleod Road for a pedestrian crossing the road, making our speed zero. The entire time I was behind this black sedan in the left lane. There were no other cars but ours on the road which made for an easy drive, which is probably why in my case I completely forgot the school zone for this area is from 2.30pm to 4pm. The cop was approximately 240m away from us,sitting on the intersection of Douglas (the U turn/cut through lane) facing us with his lights on. From his position if he were booking us from within that 240m distance I get the following numbers:
I drive a 2016 Mazda 2, it does 0 to 100 in 9.4 seconds (conservatively, I've read 10 seconds elsewhere, but I'll give the cop the conservative benefit).
100km/h —> 9.4s
60km/h (detected) —> X
X = 5.64 seconds for me to get to 60km/h.
Speed = Distance/Time
S = 240m/5.64 seconds
S = 42.55km/h is what I could've complete that 240m in, someone please correct me if I'm wrong.
I figure he had somewhere to go, so I slow down for him, he overtakes me getting between the black car and mine. He's driving behind the black car with his lights on, but no siren. As the red light for Station Road and Main Road West intersection starts to build up traffic, to my surprise he and his female partner get out of the Golf police wagon. He walks towards me and his female partner goes to the car ahead.
Being WFH for so long and never being out, I forgot that school zones (70km down to 40km) were a thing as I am never in the area during that time. He asks for my license and checks my record. I've been driving for 10 years and have never been booked - never paid a single fine, never had a single demerit. I am also fully aware I have a <15km warning available to me.
He says I was doing 60km in a 40 zone (58 alleged), however, I was behind the black car the was pulled over the entire time so I can't see how he'd be able to get a clear reading on me using a radar, a Stalker DSR (357). Looking into this radar, I can see that it does cross lane road detection, but not a car behind another car detection in the same lane. I acknowledge that I was speeding, but not at the speed that he had indicated as I believe that the speed that he has slapped me with is actually the car in front, and if my feeling is right, I would've definitely been under 55km/h which would make my first warning valid.
The fine is $330 and 3 demerit points. I am thinking of contesting it having reasonable doubt for the radar reading for being for the both of our cars, especially with mine behind the black car. However, I'm not sure if the court costs are worth it, if I do pay I'll be on 9 demerit points, $330 less and my 10 year record blemished and my first warning invalid for another 2 years. Can anyone criticize or offer thoughts or experiences?
Only if speed is constant.
Your speed was not. You were accelerating from stand still.
It would therefore make sense for your final speed (at the end of the 240m stretch) to be higher than your "would-be average speed".
Honestly, pay the fine and move on.
Edit: btw, your speed calculation is wrong
Average speed S = 240m/5.64 seconds = 42.55 m/s which is equivalent to 153.18 km/h
So yeah, I wouldn't use your calculations or measurements to fight it.
Edit2: I can see that you calculate your X using 0.6*9.4s = 5.64s
That's only true if acceleration is constant. I don't consider myself mechanically minded but cars don't do that, with engines' peak torque and what not.