Traffic forecasting terminology: the volume of traffic that would immediately use a new or improved road facility as soon as it is opened to traffic is called what?

Introduction / Context:
In project appraisal and forecasting, it is useful to separate traffic into components that reflect different sources and timings of demand. This classification guides economic evaluation, staging, and risk analysis. One such component is the traffic that will use the facility immediately upon opening.

Given Data / Assumptions:

• New or improved link opens to service.
• Some traffic shifts from existing parallel or inferior routes instantly.
• Other components accumulate over time (growth or development).

Concept / Approach:
“Current traffic” refers to existing trips already occurring in the corridor that will divert to the improved facility at opening due to lower travel time/cost or better reliability. This is distinct from “development (generated) traffic,” which arises from land-use changes enabled by the project, and from “normal traffic growth,” which is the natural increase of existing demand over future years due to population/income growth independent of the project.

Step-by-Step Solution:
Identify the immediate post-opening users: existing trips switching routes. Classify this as “current (diverted) traffic.” Exclude development/induced traffic (future response to improved accessibility) and normal growth (temporal trend).

Verification / Alternative check:
Feasibility studies often tabulate base-year diverted traffic separately from generated and growth components to avoid double counting and to assess benefits attributable to each source.

Why Other Options Are Wrong:

• Development traffic: appears later due to induced demand from land-use changes.
• Normal traffic growth: gradual increase of existing flows, not immediate at opening.
• General/Seasonal: vague categories not tied to the post-opening diversion concept.

Common Pitfalls:

• Conflating “diverted” with “generated” traffic in benefit–cost calculations.

Final Answer:
Current traffic (existing/diverted at opening).