Course Introduction and Two- Lane Highway Horizontal Alignment Lecture 1: CE 578 Highway Traffic Operations

Course Topics Highway traffic operations –Two-lane highway emphasis (40%) –Remainder on freeways (60%)

Course Website Address: Organization –Syllabus –Schedule –Assignments –Course materials –Evaluation

Course Website (cont.) Purpose: course materials delivery –Assignments –Solutions –Class reading –Announcements –Software files –Class policy –Exam schedule

Course Grading A≥90%; 90%>B ≥80%;80%>C ≥70%; 70%>D ≥60%; 60%>F Grade is based on: –Projects (20%) –Twelve mini-exams (60%) –Final exam (20%) –Assignments not graded

Horizontal Alignment Purpose: Review primary design elements Objectives –Design circular curve alignment –Estimate design speed of circular curve

Circular Curve Alignment Labels and Terms –Point of curvature (PC) –Point of tangency (PT) –Point of intersection (PI) –Curve length (L) –Curve Radius (R) –External angle (Δ) –Tangent (T)

Circular Curve Equations Tangent Curve length Station of PC and PT

Circular Curve Design Speed Side friction (f s ) Curve radius (R) Gravity constant (g)  32.2 ft/sec 2 Superelevation (e)

Circular Curve Design Speed Maximum Side friction standard values (AASHTO Green Book (pp. 147) Design Speed (mph) fsfs

Circular Curve Design Speed Superelevation  expressed as rise over run Plan View Cross-Sectional View 1 ft e A A A A

Assignment Horizontal curve alignment (circular) –Verify the following are correct for a given design on US 12 at curves with PC and PC , given the curve radius, curve PC, and external angle PI (not shown in plans), T, PT, and L. Estimate the design speed for the above curves, given the plan sheet superelevations and radius (note: superelevation for the first curve is 0.1’/ft)