PTdog

PTdog (Public Transport watchdog) helps riders see lift, escalator, and ramp conditions across key Klang Valley stations, built with accessibility in mind

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PTdog

PTdog is a public transit accessibility watch for Klang Valley. It helps riders, carers, volunteers, and station teams see when a station is difficult to use, compare a faster route with a safer one, and share updates from the ground.

About the Project

Inspiration

Trip planners are good at showing where trains go, but they usually do not show whether a station is actually usable right now. A broken lift, a blocked ramp, or a crowded interchange can turn a technically valid route into a failed trip.

PTdog was inspired by that gap. We wanted to build something small but practical:

  • a live ledger of station accessibility conditions
  • a map that makes trouble spots easy to scan
  • a route planner that values usability, not just speed
  • a simple reporting loop so the next rider has better information

What the app does

PTdog focuses on three core jobs:

  • Show current station conditions for lifts, escalators, ramps, and crowding
  • Compare the fastest route with a safer, step-free-biased route
  • Let people add fresh reports when conditions change

The result is a tool that answers a more useful question than "is there a route?"

It answers: "can I actually complete this trip?"

How we built it

The app is built as a small full-stack TypeScript project:

  • React 19 + Vite for the interface
  • Express for the backend API
  • Leaflet for the station map
  • shared TypeScript types in shared/ledger.ts
  • persistent report storage through a local JSON file, with optional Google Cloud Storage fallback

The frontend presents:

  • station cards with status summaries
  • an inspection panel with recent reports
  • a reporting form for new accessibility notes
  • a planner that compares route choices

The backend handles:

  • station seed data
  • report validation
  • merged station status
  • dispatch notes and metrics
  • persistence for user-submitted reports

We also added GTFS utilities so the project can grow beyond a static demo and connect to richer transit data over time.

Route logic

The route planner is intentionally simple. Each path cost is treated as travel time plus accessibility risk:

$$ \text{cost(path)} = \sum_{e \in path} t_e + \sum_{s \in path} p(s) $$

Where:

  • (t_e) is travel time across each connection
  • (p(s)) is a penalty based on station condition
  • critical stations can be avoided entirely in step-free mode

That lets PTdog distinguish between the fastest path and the most usable path.

Challenges we faced

  • Translating messy real-world accessibility problems into a clean data model
  • Designing a status system that is simple enough to read quickly but still useful
  • Making route logic feel practical without pretending to be a full transit engine
  • Keeping the reporting flow lightweight so users can contribute without friction
  • Balancing a polished interface with honest constraints in the current demo scope

What we learned

  • Accessibility data is only useful if it is timely and easy to trust
  • A small amount of structured ground-truth reporting can be more valuable than a polished but static map
  • "Fastest route" is often the wrong default when physical access is the real constraint
  • Good product framing matters: this is not just a map, and not just an incident board, but a decision tool

Project Structure

src/              Frontend app
server/           Express backend, ledger logic, GTFS helpers
shared/           Shared TypeScript types
data/             Local persisted report store
dist/             Production build output

Run Locally

Prerequisites: Node.js

  1. Install dependencies: bash npm install
  2. Start the app: bash npm run dev
  3. Open the client in your browser. Vite will usually serve it on http://localhost:3000 or the next free port.

Optional Environment Variables

PTdog runs without extra configuration for local use, but these variables are supported:

PORT=4000
PTDOG_LEDGER_FILE=data/ledger-store.json
PTDOG_GCS_BUCKET=your-bucket-name
PTDOG_GCS_OBJECT=ptdog/ledger-store.json

Why this project matters

Accessible transit is not only about whether infrastructure exists. It is about whether that infrastructure is working when people need it.

PTdog is a small attempt to make that visible.

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