Abstract Manager

The Mackenzie King Bridge is a four-span continuous structure extending from Elgin Street to Nicolas Street in downtown Ottawa, spanning over the National Arts Centre, Lawrence Freiman Lane, the Rideau Canal, Colonel By Drive, Rogers Centre, National Defence building, and Nicholas Street. Rehabilitation of the bridge structure triggered a full re-examination of the deck cross-section to improve active transportation by integrating raised cycle tracks and widen sidewalks within a highly constrained envelope.

An important outcome of this project was the development and first implementation of a new cast-iron tactile delineator plate specifically designed to separate sidewalks and cycle tracks where conventional half-height curb separation is not feasible. For this bridge, the City of Ottawa’s preferred curb-based separation solution was not feasible requiring a grade raise that conflicted with:

• Load restrictions on the existing structure(s)
• The introduction of grading and drainage constraints within a relatively flat deck environment
• Limited deck structural depth, restricting embedment opportunities with sensitive under-bridge uses and constraints

The delineator plate was conceived as a flat, embedded separation element that:

• Provides a continuous, tactilely detectable edge for people with low or no vision
• Is clearly distinguishable from standard tactile walking surface indicators (TWSIs) and directional/guidance indicators, to avoid misinterpretation
• Adds minimal dead load and preserves existing grades to respect structural and drainage limitations
• Is robust and compatible with winter maintenance and mechanical sweeping, and minimizes impacts on cyclist comfort and safety

Working with accessibility experts and a Canadian foundry supplier, the project team led a Pilot Project for a full product development cycle, including:

• Geometric and texture design of the plate (height, pattern, spacing) to balance detectability, ride quality, and constructability
• Prototype development using 3D-printed samples for review, testing, and refinement
• Field testing and evaluation with CNIB and other accessibility stakeholders to validate detectability and distinguishability from other TWSIs
• Refinement of material type, finish, anchoring and detailing to ensure durable integration with the concrete bridge deck

The resulting delineator plate is envisioned as a repeatable design tool for transportation engineers facing similar constraints on bridges and other constrained urban corridors, where flush or near-flush solutions are required but clear, accessible separation remains essential.

This presentation will focus on:

• The engineering problem that necessitated a new delineator solution
• The technical design, testing, and detailing of the plate system
• Lessons learned from piloting a new tactile product in a complex urban bridge renewal
• How this delineator can be applied as an alternative separation treatment in other constrained active transportation projects