luokai0 Transportation Engineering Expert
Before Starting
- Highway design or traffic operations?
- New facility or existing system analysis?
- Urban or rural context?
Core Expertise Areas
Traffic Flow Theory
Flow, speed, density: q = k times u, fundamental flow relationship. Greenshields model: linear speed-density relationship, parabolic flow-density. Capacity: maximum sustained flow rate, varies by facility type. Level of service: A through F rating of traffic operations quality. HCM: Highway Capacity Manual, standard methods for capacity and LOS analysis.
Highway Geometric Design
Horizontal alignment: tangents and circular curves, superelevation. Stopping sight distance: based on design speed, reaction time, braking distance. Vertical alignment: grades and crest and sag vertical curves. Cross section: travel lanes, shoulders, medians, clear zones, slopes. Design speed: governs all geometric design elements.
Intersection Design
At-grade intersections: signalized, stop-controlled, yield-controlled. Signal timing: cycle length, phase splits, offsets for coordination. Roundabouts: yield at entry, continuous flow, fewer conflict points than signals. Interchange types: diamond, cloverleaf, directional for grade separation.
Pavement Design
Flexible pavement: asphalt surface on granular base, AASHTO design method. Rigid pavement: concrete slab on base, controls deflection and cracking. ESAL: equivalent single axle load, accounts for different vehicle weights. Pavement condition: IRI, PCI, distress surveys for maintenance planning.
Best Practices
- Collect actual traffic counts before designing improvements
- Check sight distance at all critical locations
- Design for design year traffic not just current conditions
- Consider pedestrian and bicycle needs in all transportation design
Common Pitfalls
| Pitfall | Fix |
|---|---|
| Ignoring pedestrians in signal timing | Include pedestrian crossing time in phase lengths |
| Insufficient sight distance on curves | Check both stopping and passing sight distance |
| Underdesigned pavement for actual trucks | Use actual axle load data for ESAL calculations |
| Wrong LOS method for facility type | Use HCM method specific to facility type |
Related Skills
- structural-engineering-expert
- hydraulics-expert
- construction-management-expert