• Inelastic Demand ($|E| < 1$): Travel demand changes less than proportionally to price changes. A large increase in price causes only a small drop in demand. For example, a 10% increase in a toll might only cause a 2% drop in traffic on that route. Commuter trips and necessary work travel are often highly inelastic in the short term, as people have few immediate alternatives to getting to work.
• Elastic Demand ($|E| > 1$): Travel demand changes more proportionally to price changes. A small increase in price causes a large drop in demand. For example, a 10% increase in a bus fare might cause a 15% drop in ridership. Discretionary trips (like weekend shopping or recreation) or trips where easy alternatives exist (e.g., driving vs taking a parallel train) are more elastic.
• Cross-Elasticity: The responsiveness of demand for one mode to a price change in another mode. For example, how much does train ridership increase if the cost of parking downtown increases by 20%? A positive cross-elasticity indicates the modes are substitutes.

• Work/Business Trips: Time saved during working hours is typically valued at the traveler's full hourly wage rate plus overhead, as that time could have been spent producing economic output.
• Commute/Personal Trips: Time saved on personal time is usually valued at a fraction of the average wage rate (e.g., 30% to 50%), representing the traveler's 'willingness to pay' to avoid sitting in traffic.
• Freight: Valued based on the driver's wage plus the time-sensitive value of the cargo (e.g., fresh produce has a higher VOT than coal).

Assuming all future costs and benefits have been converted to their Present Value ($PV$):

• Net Present Value (NPV): Decision Rule: Accept the project if $NPV > 0$. When comparing mutually exclusive alternatives, choose the one with the highest NPV.
• Benefit-Cost Ratio (B/C Ratio): Decision Rule: Accept the project if $B/C \ge 1.0$. This means for every dollar spent, the public gets at least one dollar back in benefits.
• Internal Rate of Return (IRR): The specific discount rate ($r$) that makes the $NPV$ exactly equal to zero. Decision Rule: Accept the project if the $IRR$ is greater than the agency's Minimum Attractive Rate of Return (MARR).

• Consumer Surplus: The difference between the maximum price a traveler is willing to pay for a trip and the actual generalized cost they incur. A new, faster highway lowers the generalized cost, thereby increasing the consumer surplus (creating an economic benefit).
• Producer Surplus: The difference between the revenue received by the transport provider (e.g., toll operator, transit agency) and the cost of providing the service.

LCCA proves mathematically that spending more upfront for higher-quality materials (e.g., a thicker concrete pavement instead of cheap asphalt) often results in a lower total cost of ownership over a 40-year horizon because it avoids frequent, highly disruptive maintenance cycles.

• The Highway Trust Fund & Gas Taxes: Historically, the U.S. federal government funded infrastructure via the Highway Trust Fund, replenished almost entirely by a per-gallon federal fuel excise tax. This acts as a rough "user fee"—the more you drive, the more you pay. However, as vehicle fuel efficiency increases and EVs proliferate, gas tax revenues have precipitously declined, rendering the fund technically insolvent without general taxpayer bailouts.
• Vehicle Miles Traveled (VMT) Fees: A proposed replacement for the gas tax. Drivers are charged a per-mile fee based on distance traveled, regardless of their vehicle's fuel efficiency. This requires tracking technology (e.g., GPS or odometer readings) and raises privacy concerns.
• Tolling and Congestion Pricing: Charging drivers directly for the use of specific roads or zones (e.g., a downtown cordon). This provides a direct, highly stable revenue stream and can simultaneously be used to manage demand (charging more during peak hours). Electronic Toll Collection (ETC) has made this highly efficient.
• Public-Private Partnerships (P3s): Long-term contracts between a government agency and a private consortium. The private entity designs, builds, finances, operates, and maintains (DBFOM) the infrastructure in exchange for the right to collect tolls or receive availability payments from the government. P3s shift the massive upfront capital costs and long-term maintenance risks off the public balance sheet.