Traffic and Accident Analysis - Answers

I marked these pages:

Headway, Spacing, Volume - Section 10 - Page 74-6

Warrants for signal - Section 16 - Page 74-14

I also downloaded some info from the HCM 2000 - in the form of class notes regarding the designs for 2 lane highways and multiland highways - I didn't feel like the info in the book was enough, especially since the answers to the questions kept referencing HCM.

Today's Answers:

Traffic and Accident Analysis - Questions

I am studying the material in Chapter 74, but the questions require the use of HCM, which I do not currently have, so I am not able to post questions, since I’m am unsure I will be able to answer them.

For Chapter 75 though – I present these 2:

1. Two cars are moving at 50 mph in the same directions in the same lane. The cars are separated by 20 ft per 10 mph. The coefficient of friction (skidding) is 0.65. The reaction time is assumed to be 0.4 sec.
a) If the lead car hits a parked car, what is the speed of the second car when it hits the first car?
b) If the lead car hits a parked car and comes to an abrupt halt, at what speed does the rule of 1 car length (20 ft) per 10 mph of speed become unsafe?
c) At 60 mph what should the rule actually be?

2. Two vehicles collide head on while traveling a curve with a 4% grade. Vehicle A skidded 200 feet downhill before colliding with vehicle B. Vehcile B skidded 150 ft. The police report estimates both car traveling at 30 mph prior to the collision. Assume a coefficient of friction of 0.5.
a) What was the speed of vehicle A prior to hitting the brakes?
b) What was the speed of vehicle B prior to hitting the brakes?
c) Which assumption produces the greatest possible error?

Traffic and Accident Analysis

Chapters 74 and 75 in Lindeburg



Chapter 74 - Roads and Highways : Capacity Analysis - 6 Problems

Chapter 75 - Vehicle Dynamics and Accident Analysis - 4 Problems

Highway Curves - Answers

I marked these pages:

Stopping Sight Distance - Table 79.2 - Page 79-10

Today's Answers:

Highway Curves - Questions

1. Use the following diagram:

a) At what station is the low point located?
b) At what elevation is the low point?
c) At what elevation is the sta 21+75.05
d) What is the highest design speed for the curve?
e) What is the rate of grade change per station?
f) If 18 ft of clearance is required, what is the lowest elevation that the bottom of an overhead bredige deck may have at sta 22+75

2. The grades on a vertical curve intersect at station 110+00 and elevation 352 ft. A drain grating exists at sta 110+00 at elevation 360.25 ft

a) Given a curve length of 1800 ft, what is the elevation of BVC?
b) Given a curve length of 1800 ft, what is the elevation of sta 111+40?
c) Given a curve length of 1800 ft, what is the elevation of the low point?
d) Given a curve length of 1800 ft, what is the station of BVC?
e) Given a curve length of 1800 ft, what is the elevation of EVC?

3.
The tangent of the horizontal curve shown is relocated 12 ft west of its original position. The PC remains the same.
a) What is the original curve radius?
b) What is the new curve radius?

Highway Curves

Chapter 79 in Lindeburg


Chapter 79 - Horizontal, Compound, Vertical, and Spiral Curves - 15 Problems

Surveying - Answers

I marked these pages:

Errors (Survey) - Section 1 ---> - Page 78-1

Elevation corrections - Section 18 - Page 78-9

Today's Answers:

Surveying - Questions

1.
Errors
Four level circuits were run over four different routes. The elevation and error for each circuit is listed below. What is the most probably value of the benchmark’s elevation?

Route 1: 745.07 ± 0.02
Route 2: 745.22 ± 0.03
Route 3: 745.40 ± 0.08
Route 4: 745.16 ± 0.04

2.
Leveling
A level is placed where the height of the instrument above datum is 294.45 ft. The rod is held on a point 4000 ft away. And a reading of 4.65 ft is recorded.
a) Find the effect of the earth’s curvature on the rod reading
b) Find the effect of the atmospheric refraction on the rod reading.


3.
A 5 leg closed traverse is taped and scoped in the field, but obstructions make it impossible to collect all the readings. It is known that the general direction of EA is east west. Complete the field notes:

Leg north azimuth distance
AB 106.22° 1081.3
BC 195.32° 1589.5
CD 247.12° 1293.7
DE 332.37° ______
EA ______° 1081.3


4.
Photogrammetry
A camera with a focal length of 5 inches and a size of 10 in by 10 in is used to photograph an area from an altitude of 4500 ft above sea level.
a) If the average elevation is 600 ft, what is the average scale of the photo?
b) What is the ground area covered by a single photograph?
c) If overlap and sidelap are 50% and 30% respectively, what is the ground spacing between exposures?
d) same as c) what is the ground spacing between flight lines?
e) if the aircraft is moving at 325 mph ground speed, what is the time interval to the nearest 0.1 sec between exposures?
f) two points at elevation 650 ft appear 90 mm apart on the photo, what is the ground distance?
g) what elevation should a plane be flown to get an average scale of 1:10,000 if the elevation is 1100-1300 ft above sea level.

Surveying

Chapter 78 in Lindeburg



Plane Surveying - Chapter 78 - 9 Problems