Transportation Engineering Tutoring

Transportation engineering covers how people and goods move, and how roads are planned, designed, and operated. A typical course mixes three kinds of work. Traffic engineering uses flow, speed, and density to study how a road performs. Geometric design lays out curves, grades, and sight distances for safe travel. Planning asks how many trips there will be and which routes they will use. The math is moderate, but there are many formulas, and the courses lean on design manuals as much as on theory.

Sessions follow your textbook, often Garber and Hoel, Mannering, or Roess, Prassas and McShane, along with the manuals your course allows, such as the AASHTO Green Book and the Highway Capacity Manual. We practice the standard problem types until each one has a clear routine, and we keep a short list of the formulas, units, and assumptions that cause the most lost points.

A typical transportation problem, worked

A horizontal curve is designed for 60 mph with a maximum superelevation of 6 percent and a side friction factor of 0.12. The deflection angle is 40 degrees. Find the minimum radius, the curve length, and the tangent length.

The minimum radius is $$R = \dfrac{V^{2}}{15(e + f)} = \dfrac{60^{2}}{15 \times (0.06 + 0.12)} = \dfrac{3{,}600}{2.7} = 1{,}333\ \text{ft}$$

Curve length is $$L = R \times \Delta\ \text{(in radians)} = 1{,}333 \times \left(\dfrac{40 \times \pi}{180}\right) = 1{,}333 \times 0.698 = 931\ \text{ft}$$

Tangent length is $$T = R \tan\left(\dfrac{\Delta}{2}\right) = 1{,}333 \times \tan\left(20^\circ\right) = 1{,}333 \times 0.364 = 485\ \text{ft}$$ In a real design, $e$ and $f$ come from the current design tables, and the radius is rounded up to a practical value.

Where students usually get stuck

• Mixing mph with ft/s, or feet with miles, in stopping distance and curve formulas
• Choosing the right Highway Capacity Manual method and reading the correct table
• Station and curve geometry, where PC, PI, and PT points are easy to confuse
• Signal timing: finding the critical lane groups and the lost time
• Four-step model problems, where each step feeds the next