Student’s Guide

Collision Investigation (1-D)

SPVM File # 990827-32

Camil Cyr

Collège de Maisonneuve

Adaptation: Nanouk Paré

John Abbott College

Collision Investigation (1-D)

SPVM File # 990827-32

Context

You are just starting a summer job for Montreal Police (SPVM) collision investigators. You assist the investigatorsin order to determine, as accurately as possible, the circumstances surrounding collisions (initialvelocity of the vehicles involved, direction vehicles were heading, etc.) in order to take action againstdrivers at fault under the Criminal Code (dangerous driving causing death or other charges). The job isdemanding and your help is highly appreciated.

The weather is great, it’s July, and you arrive at the stationas your boss tells you, “Hey, Rookie, hurry over toNotre-Dame Street. There has been an accident involving two cars. There are people injured.” Listening only to yourcourage, you rush (although carefully) to the scene of theaccident. Your job is to take photos of the vehicles as theyare positioned, and take a certain number of measurements,including the length of the skid marks and layout ofthe debris. You immediately draw the following sketch ofthe accident and include a few common measurements.

Your findings are as follows:

•Numerous debris (broken glass, plastic, etc.) were found at a distance of 12.25 m from the cars;

•The two cars stuck together and there are skid marks over 12.25 m;

•There are also skid marks over a distance of 30 m before the debris;

•The posted speed limit on this street is 70 km/h;

•Other data: m1 = 2.674 kg, m2 = 1.100 kg.

1-D Collision Investigation (Part 1)

A hurried investigator yells out, “Hey, Rookie, make yourself useful! Bring the friction block and spring scale, and take the measurements needed to calculate the pavement’s coefficient of friction.” Confused, but very eager, you take the heavy iron friction block, covered with tire treads, and the spring scale.

•Which parameters can be obtained by using the friction block and spring scale?

•Based on this information about the method used, find an equation that allows you to determine thepavement’s coefficient of friction.

Complete the three-step cycle to get a clear picture of what we know, what we need to know, and thesummary.

Three-Step Cycle

List all the revelant information you have gathered from the problem. Based on this information, statewhat you need to know to solve the problem. As new information comes in, you will want to summarizeand update the relevant information you have gathered and ask new questions.

What we know / What we need to know / Summary

List the following:

Please note: You must complete the Part 1 before proceeding to the Part 2.

1-D Collision Investigation (Part 2)

Here are the two measurements (Fv: vertical force, Fh: horizontal force) that you obtain from the frictionblock and spring scale. They will enable you to determine the pavement’s coefficient of friction.

Fv = 88,2 N and Fh = 75,8 N

The investigator returns to you and says, “The two drivers aren’t saying much. The one in the small redcar was sent to the hospital. The driver in the yellow car is still discussing what happened, but nothingis clear!” Since you are always willing to help, you answer, “How can I help you, Sir?” The investigator’sface lights up when he hears your proposition, “Well, it’s that…, you see, we must be sure, beyond any doubt, that dangerous driving was involved… the judge needs evidence. We must gather all the necessaryevidence. All I’m sure of is that, based on the skid marks, the red car was at the stop when the collisionoccurred. This a perfect job for an intern! Get to work! I want a full report ASAP”. Knowing that thisinformation will enable the Crown prosecutor to decide whether the driver will be charged under Section249 (3), Dangerous driving causing bodily harm, of the Criminal Code, you take your role very seriouslyand immediately get to work.

Considering that the accident occurred in a 70km/h zone, what do you suggest to your superior? Presscharges for dangerous driving or not? If the Crown prosecutor asked you to testify in court, how wouldyou clearly explain to the judge and jury the method used to determine the speed of the driver at fault?

PBL/Student’s Guide - Collision Investigation (1-D) / SPVM File # 990827-321