Traffic Investigation

Level 2

WITNESS STATEMENTS

Craig (not riding a bike): 4 motorcycles were east on 64 Ave. approaching 54th St. NE. As the bikes were going through, a Mercedes went through, not seeing the bikes. Three bikes went left, one went right and hit the car.

Looking East, 64th Ave.

WITNESS STATEMENTS

Steve: We were going down 64th Ave. approaching the intersection when a car pulled up to a stop sign and slowed down but did not stop and proceeded through the intersection. Rob, the victim, tried to swerve out of the way to the left and hit her front left side. She did not even see us coming. I was going 65 km/h.

POSTED SPEED LIMIT

WITNESS STATEMENTS

Mike: We were driving down 64th Ave. approaching 54th St. when I saw a car merge out of Martindale Road without completely stopping at the stop sign. The driver DID NOT EVEN SEE US AT ALL BECAUSE SHE NEVER LOOKED. Rob swerved to the left and hit the car on the left side. He flipped in the air twice and got up, then dropped down again. She then got out of the car and walked away.

WITNESS STATEMENTS

Todd: I saw a car do a rolling stop at the stop sign on the north side on 54th St. I braked and missed the vehicle and looked to see Rob hit the car on the front driver’s side. We were doing about 50-55 km/h.

WITNESS STATEMENTS

Mercedes driver: I left church and was coming to my house. I stopped at the stop sign on 64 Ave. After coming to a stop, I looked both ways, left and right, for oncoming traffic. After making sure there was no traffic, I started to move across 64th Ave. but suddenly a motorcycle came from no where at a very high speed and hit my car. My car turned from south to west with the collision.

PERSPECTIVE OF MERCEDES DRIVER

WITNESS STATEMENT

Rob: I was westbound on 64th Ave. and as I came close to 54th Ave, I saw a car nearing the intersection so I slowed down a bit. Thinking the car would stop, I continued through the intersection. The car went through very slowly. I didn’t have time to stop and hit the front end. I was in the left lane of the road. When I noticed the car I was going about 60 km/h. Before I hit, I tried to steer to the left.

SYNOPSIS

At 1355 hours on April 24, 4 motorcycles were westbound on 64th Ave. NE approaching Martindale Road. A gray Mercedes was southbound on Martindale Road and approached a stop sign at 64th Ave. The Mercedes entered the intersection as the motorcycles approached and 3 of the 4 motorcycles veered to the south.

SYNOPSIS, cont.

The 4th cyclist, who was in the center lane, veered to the south in an attempt to avoid the car and collided with the left front corner of the Mercedes. The cyclist was vaulted from his motorcycle and landed in the eastbound lanes of 64th Ave. The cyclist suffered from road burns to his legs and arms and the driver of the Mercedes suffered a broken right arm and small laceration to the head.

OBJECTIVES OF RECONSTRUCTION REPORT Determine the coefficient of friction for the

roadway surface of 64th Ave. Determine the minimum speed for the eastbound

motorcycle at the start of the skid. Determine the speed of the motorcycle at impact. Determine the stopping distance for the

motorcycle at:a. The posted speed limit.b. The calculated speed.

(Use 100% braking efficiency)

COEFFICIENT OF FRICTIONS (FASTER THAN 50 KM/H)

Road Surface Dry Wet

Concrete (traveled)

0.60-0.80 0.45-0.65

Asphalt or tar (traveled)

0.40-0.70 0.40-0.65

Gravel (packed, oiled)

0.50-0.80 0.40-0.60

Ice (smooth) 0.07-0.20 0.05-0.10

Snow (packed) 0.35-0.55 0.30-0.60

COEFFICIENT OF FRICTION

Roadway cooled drag sled pulled east to west adjacent to the motorcycle tire mark.

COEFFICIENT OF FRICTION

35 lb sled pulled by constable 10 pulls were conducted: 22 lbs. 21 lbs. 22 lbs. 21 lbs. 21 lbs. 21 lbs. 21 lbs. 21 lbs. 20 lbs. 22 lbs Average pull: 21.2

SAMPLE FORMULAE

f = F/W S = (30df)1/2

S = (2ad)1/2

d = St

Where f is the coefficient of friction, d is distance, a is acceleration, s is speed, W is weight, F is force.

COEFFICIENT OF FRICTION

W = 35 lbs. F = 21.2 lbs. Ff = FN

= Ff /FN = 21.2lbs./35 lbs. = 0.60

MINIMUM SPEED FOR MOTORCYCLE AT START OF SKID

Bike left a rear tire only skid mark 17.70 m long.

d = 17.70 m = 0.60 S = 297/ (d)() S = 28 km/h

The bike lost 28 km/h prior to impact with the vehicle.

MINIMUM SPEED FOR MOTORCYCLE AT IMPACT After impact, M/C rider was vaulted 7.60 m

from take off point. The seat height was 0.79 m.

d = 7.60 m h = 0.79 m S = 11.27(d) = (11.27)(7.60 m) = 29 km/h

d h 7.60 m + 0.79 m

Motorcycle was traveling at 29 km/h at the time of impact.

MINIMUM SPEED FOR MOTORCYCLE AT IMPACT

S1 = 28 km/h

S2 = 29 km/h

S2 = S12 + S2

2

S2 = 40 km/h

The speed of the motorcycle at brake application was calculated to be 40 km/h.

MINIMUM STOPPING DISTANCE FOR MOTORCYCLE

Speed limit = 60 km/h d = S2/ (254)() d = (60 km/h)2/(254)(0.60) d = 23.62 m

The motorcycle required 23.62 m to come to a stop using 100% braking at the posted speed limit.

MINIMUM STOPPING DISTANCE FOR MOTORCYLCE, CONT.

S = 40 km/h d = S2/(254)() d = (40 km/h)2/(254)(0.60) d = 10.49 m Rider would require 10.49 m to come to a

stop using 100% braking at the calculated speed of 40 km/h.

CONCLUSION AND OPINIONS

It is the opinion of the traffic reconstructionist that the vehicle left the stop sign when it was unsafe to do so. However, based on the motorcycle rider locking the rear wheel only, the stopping distance was greatly increased. Had the rider made an emergency 100% brake application (front and rear), he would have been able to stop well short of the impact location.

CONCLUSION AND OPINION, CONT.

Had the rider been traveling at the posted speed of 60 km/h, he would have required 23.62 m to stop. This would have taken him into the impact zone, but at a much lower impact speed. This would have reduced his injuries.

Finale

The automobile driver is responsible for entering the road when unsafe, but a rider with more experience/training may have been able to stop in time or slow down a great deal prior to impact.