Highway planning and traffic studies: traffic surveys are typically conducted for which of the following purposes?

Introduction / Context:
Traffic surveys underpin every stage of highway planning, design, and operation. They capture how many vehicles travel, what types they are, when and where they move, and how they interact with the roadway and environment. This information informs capacity, safety countermeasures, geometric features, and even drainage provisions that depend on lane configurations and pavement width.

Given Data / Assumptions:

• Surveys may include volume counts, origin–destination, classified counts, speed and delay, parking, axle loads, and pedestrian studies.
• Outputs feed both design and operations decisions.

Concept / Approach:
Traffic type and composition (option a) affects lane width, pavement thickness (via ESALs), and intersection control. Regulatory needs and facilities (option b) such as signals, signs, channelization, crossings, and access control depend on observed flows, speeds, and conflicts. Roadway drainage and appurtenances (option c) relate to cross-section elements like shoulders and medians; traffic data influence these through the chosen standards and pavement extents, which, in turn, guide drainage sizing and placement.

Step-by-Step Solution:
Recognize that traffic composition and demand are core survey outputs. Connect survey results to regulatory/control facility needs. Acknowledge that cross-section and paved area decisions affect hydrology; surveys indirectly inform drainage design. Hence, all the listed purposes are valid.

Verification / Alternative check:
Feasibility reports and DPRs routinely include traffic surveys that later inform geometric standards, pavement design, roadside drainage, and traffic management plans.

Why Other Options Are Wrong:

• Any single choice understates the broad, multi-disciplinary role of traffic surveys.
• “None” is incorrect because the purposes listed are standard practice.

Common Pitfalls:

• Using short-duration counts without seasonal/weekly adjustment factors, leading to mis-sized facilities.

Final Answer:
All the above.