CEE320 Midterm Exam 10 True/false (20% of points) 4 Short answer (20% of points) 3 Calculations (60% of points) –Homework –In class examples

Course material covered Introduction Vehicle dynamics (chapter 2) Geometric design (chapter 3) Pavement design (chapter 4 except 4.3, 4.5, including 4 th power thumbrule)

Suggestions for Preparation Review each lecture and identify the main points and formulas. Write these on summary notes. For each lecture, write an question. Do this in a group, and share questions. Solve these questions from scratch, do not just review solutions. Review homework and in class examples. Do the problem yourself. Make a list of the tables in the text, their title, and the page number. Include a note of what it is used for.

Transportation Engineering The science of safe and efficient movement of people and goods

Road Use Growth From the Bureau of Transportation Statistics, National Transportation Statistics 2003

Sum forces on the vehicle

Aerodynamic Resistance R a Composed of: 1.Turbulent air flow around vehicle body (85%) 2.Friction of air over vehicle body (12%) 3.Vehicle component resistance, from radiators and air vents (3%) from National Research Council Canada

Power required to overcome R a Power –work/time –force*distance/time –R a *V

Rolling Resistance R rl Composed primarily of 1.Resistance from tire deformation (  90%) 2.Tire penetration and surface compression (  4%) 3.Tire slippage and air circulation around wheel (  6%) 4.Wide range of factors affect total rolling resistance 5.Simplifying approximation:

Grade Resistance R g Composed of –Gravitational force acting on the vehicle –The component parallel to the roadway For small angles, θgθg W θgθg RgRg G=grade, vertical rise per horizontal distance (generally specified as %)

Engine-Generated Tractive Effort FeFe =Engine generated tractive effort reaching wheels (lb) MeMe =Engine torque (ft-lb) ε0ε0 =Gear reduction ratio ηdηd =Driveline efficiency r=Wheel radius (ft) Front Wheel Drive

Braking Force Ratio Efficiency We develop this to calculate braking distance – necessary for roadway design

Braking Distance Theoretical Practical

Stopping Sight Distance (SSD) Worst-case conditions –Poor driver skills –Low braking efficiency –Wet pavement Perception-reaction time = 2.5 seconds Equation

Stationing – Linear Reference System Horizontal Alignment Vertical Alignment feet >100 feet

Vertical Curve Fundamentals G1G1 G2G2 PVI PVT PVC L=curve length on horizontal L/2 δ x Choose Either: G 1, G 2 in decimal form, L in feet G 1, G 2 in percent, L in stations

Relationships

Other Properties K-Value (defines vertical curvature) –The number of horizontal feet needed for a 1% change in slope A as a percentage L in feet

Crest Vertical Curves For S < LFor S > L

Sag Vertical Curves G1G1 G2G2 PVI PVT PVC h 2 =0 h 1 =H L Light Beam Distance (S) For S < LFor S > L headlight beam (diverging from LOS by β degrees)

Underpass Sight Distance

On sag curves: obstacle obstructs view Curve must be long enough to provide adequate sight distance (S=SSD) S<L S>L

Horizontal Curve Fundamentals R T PC PT PI M E R Δ Δ/2 L

Stopping Sight Distance RvRv ΔsΔs Obstruction MsMs SSD (not L)

Superelevation Minimum radius that provides for safe vehicle operation Given vehicle speed, coefficient of side friction, gravity, and superelevation R v because it is to the vehicle’s path (as opposed to edge of roadway)