Traffic signs (route markers): From the point of tangency (PT) before an intersection, at what typical distance are route marker signs installed to give adequate advance guidance?

Introduction / Context:
Route markers and advance guide signs must be placed so drivers have enough preview time to decide and manoeuvre safely. On approaches to intersections, the distance from the point of tangency (PT) or approach tangent affects legibility, comprehension, and lane choice.

Given Data / Assumptions:

• Urban or rural approaches with typical design speeds.
• Standard legibility distances and driver reaction needs.
• Signs are of standard size and reflectivity as per codes.

Concept / Approach:

Placement balances two needs: early enough to read and act, and not so early that the message is missed or forgotten. For common approach speeds and junction layouts, a distance on the order of tens of metres (not just a few metres, not hundreds) is generally adopted for route markers immediately ahead of the intersection, often complemented by advance direction signs farther upstream.

Step-by-Step Reasoning:

Verification / Alternative check:

Sign placement tables tie legibility to letter height and speed; 50–75 m aligns with typical fonts and speeds for route markers adjacent to intersections, while advance guide signs are located much farther upstream.

Why Other Options Are Wrong:

• 15–35 m: Drivers may not have time to read and respond safely.
• 40–50 m: Marginal at higher approach speeds.
• 100–150 m: More suited to major advance guide signs rather than small route markers just before the junction.

Common Pitfalls:

• Using one placement distance for all contexts; always consider speed and sign size.

Final Answer:

50 m to 75 m.