Fundamentals of Transportation/Conclusions

Transportation is multi-modal, multi-disciplinary field that requires the efforts of people from a spectrum of backgrounds. Planners, engineers and policy makers are the primary groups, but architects, economists, and operations researchers serve in roles that benefit the industry. In order for an idea to become a road, it must go through several planning and design stages. This section serves as a conclusion for this wikibook as well as a summary of the building process for a roadway.

Connecting Places

• Planning
• Assessing Needs: Testing Alternatives (Hypotheses)
• Predicting Demand
• Trip Generation
• Trip Distribution
• Mode Choice
• Route Assignment

Determining Road Capacity (Width)

• Level of service
• Design to satisfy standard
• Understand implications of traffic (queues, shockwaves, congestion)

Determining Road Alignment (Length)

• Properties of drivers, vehicles, roadway
• Maximum grade associated with speed, vehicle type
• Stopping sight distance
• Vertical alignment (sags & crests)
• Horizontal alignment

Determining Road Strength (Depth)

• Given load on the road, how long can the road hold up.
• Design pavement depth to satisfy predicted traffic.

Putting it together

Planning determines origin/destination demand by vehicle type … feeds into Level of Service

• LOS feeds into in-depth traffic analysis and determines number of lanes
• Truck demand determines maximum grade
• Stopping sight distance determines horizontal and vertical curvatures.
• Truck demand determines pavement thickness

Implications

Fraction of demand (trucks) is determining design characteristics (grade, depth)

Fraction of demand (peak hour traffic) is determining width.

1. Financing should consider this

2. Design should consider this. Maybe cars and trucks should have separate routes. (car-only highways would be cheaper, separation would be safer).

3. We don’t ask one building to serve all needs, why should one road?

Thought Question

How does an idea become a road? Explain how an idea becomes a road. Illustrate your explanation with a consistent set of examples for all of the major steps of analysis that are required (i.e. the output of one example should be the input to the next example).