Lecture 21 - Road and car safety

Question 1

What evidence is collected/marked in a crash investigation?

Answer 1

Tyre marks, scrape marks, fluid patches, debris and final vehicle positions

Question 2

What is analysed in a vehicle examination?

Answer 2

Exterior and interior points of contact, intrusion measurements, airbag deployment, seatbelt wearing and tyre condition

Question 3

How are tyre marks produced?

Answer 3

They are a product of friction generated heat. On a dry road the bitumen is heated and smeared and on a wet road the water is heated and removed

Question 4

What are the characteristics of skid marks?

Answer 4

Caused by vehicle braking and wheels slipping. Mostly straight with parallel striations following the tread. May have an uneven start

Question 5

What are the characteristics of yaw marks?

Answer 5

Caused by the wheel sliding and rotating at the same time. Has diagonal grooves and striations. Curved with a decreasing radius

Question 6

What are the limitations of determining travel speed from skid marks?

Answer 6

Skid marks begin about 0.1 seconds after braking begins and therefore the calculations give an underestimate on speed