Transport Modes

Overview

MND supports three primary transport modes that can be combined intelligently to create optimal multi-modal routes:

Bus

Free scheduled university buses

Local

Paid CNG/rickshaw transport

Walking

Free pedestrian movement

🚌 Bus Transport

Overview

SUST operates 7 free bus routes serving 19 locations across Sylhet city.

Bus Characteristics

Cost

Free

University buses are 100% free for students and staff

Schedule

Fixed

Buses run on fixed schedules with specific departure times:

Morning: 07:30 - 09:35
Afternoon: 13:10 - 17:10
Evening: 18:30 (limited routes)

Capacity

40-50 passengers

Standard bus capacity, can get crowded during peak hours

Speed

~5 min per stop

Average travel time between consecutive stops

Route Coverage

7 Bus Routes:

Bus 1 & 2: TILAGOR ↔ CAMPUS (via AMBARKHANA)
Bus 3 & 4: NAIORPUL ↔ CAMPUS (via JAIL_RD)
Bus 5: LAKKATURA ↔ CAMPUS
Bus 6: NAIORPUL/SHAHI_EIDGAH ↔ CAMPUS
Bus 7: SHEIKHGHAT/SHAHI_EIDGAH ↔ CAMPUS

Key Hub Stops:

AMBARKHANA (5 routes)
SUBIDBAZAR (6 routes)
CAMPUS (all routes)

Schedule Example

Bus 1 Schedule (Sample Day):

Trip ID	Direction	Departure	Route
bus1_0825	to_campus	08:25	TILAGOR → CAMPUS
bus1_0930	to_campus	09:30	TILAGOR → CAMPUS
bus1_1310	from_campus	13:10	CAMPUS → TILAGOR
bus1_1710	from_campus	17:10	CAMPUS → TILAGOR

Data Model

export interface Route {
    route_id: string;      // "bus1", "bus2", etc.
    name: string;          // "Bus 1", "Bus 2", etc.
    trips: Trip[];         // List of scheduled trips
}

export interface Trip {
    trip_id: string;       // "bus1_0825"
    direction: 'to_campus' | 'from_campus';
    stops: string[];       // Node IDs in order
    departure_time: string; // "08:25" (HH:MM)
}

Source: MND-backend/src/data/routes.json

Travel Time Calculation

Bus travel time is estimated using a 5-minute-per-hop heuristic:

// From planner.ts:98-111
const hopsBefore = fromIndex;
const tripStart = parseTime(trip.departure_time);
const tripStartMin = timeToMinutes(tripStart);

// Estimate time to reach 'from' stop
const timeToFrom = hopsBefore * 5; // 5 min average per hop
const departureMin = tripStartMin + timeToFrom;

// Calculate travel time
const hops = toIndex - fromIndex;
const travelTime = hops * 5; // 5 min per stop
const arrivalTime = addMinutes(trip.departure_time, timeToFrom + travelTime);

The 5-minute estimate accounts for driving time + stop duration. Actual times may vary based on traffic.

Color Coding: Blue

In the mobile app, bus segments are displayed in blue:

// Color mapping in Flutter app
Color getModeColor(String mode) {
  switch (mode) {
    case 'bus':
      return Colors.blue;      // 🚌 Bus routes
    case 'local':
      return Colors.orange;    // 🚕 Local transport
    case 'walk':
      return Colors.green;     // 🚶 Walking
    default:
      return Colors.grey;
  }
}

🚕 Local Transport (CNG/Rickshaw)

Overview

Local transport refers to paid, on-demand options like CNG auto-rickshaws and cycle rickshaws.

CNG Auto-Rickshaw

Characteristics:

💰 Cost: 20-50 BDT (typically ~2 BDT per 100m)
⚡ Speed: Moderate (faster than rickshaw, slower than bus)
🛣️ Range: Short to medium distances (1-5 km)
🚦 Availability: High (found everywhere in Sylhet)

When to Use:

Final mile connectivity (after bus drop-off)
Destinations not served by buses
Urgent travel (no time to wait for bus)

Cycle Rickshaw

Characteristics:

💰 Cost: 10-30 BDT (cheaper than CNG)
🐌 Speed: Slow (human-powered)
🛣️ Range: Very short distances (< 2 km)
🚦 Availability: High in residential areas

When to Use:

Very short distances
Budget-conscious travel
Areas with narrow roads (CNG can’t access)

Data Model

export interface Edge {
    from: string;
    to: string;
    mode: 'bus' | 'local' | 'walk';
    route_ids?: string[];        // Only for bus edges
    time_min: number;            // Travel time in minutes
    distance_meters?: number;    // Physical distance
    cost: number;                // 0 for bus/walk, > 0 for local
    one_way: boolean;            // Directionality
    source?: 'graph' | 'distance_matrix';
}

Cost Calculation

Local transport costs are estimated using a distance-based formula:

// From planner.ts:179
const costPerHundredMeters = 2; // BDT
const totalCost = Math.round(distanceMeters / 100) * 2;

// Example: 2000 meters = 20 × 2 = 40 BDT

This is an approximate cost model. Actual fares may vary based on:

Negotiation with driver
Time of day (night surcharge)
Traffic conditions
Shared vs. private ride

Distance Matrix Integration

When local transport segments are not in the graph, MND uses Google Maps Distance Matrix API:

// From distanceMatrixClient.ts
export async function getLocalSegment(
    from: string,
    to: string,
    mode: 'driving' | 'walking'
): Promise<DistanceMatrixResult> {
    // Check cache first
    const cacheKey = `${from}-${to}-${mode}`;
    const cached = this.cache.get(cacheKey);
    
    if (cached && !this.isCacheExpired(cached)) {
        return { ok: true, ...cached, fromCache: true };
    }
    
    // Call Google Maps API
    const response = await fetch(
        `https://maps.googleapis.com/maps/api/distancematrix/json?` +
        `origins=${from}&destinations=${to}&mode=${mode}&key=${API_KEY}`
    );
    
    const data = await response.json();
    const element = data.rows[0]?.elements[0];
    
    if (element?.status === 'OK') {
        const result = {
            distanceMeters: element.distance.value,
            durationSeconds: element.duration.value,
            timestamp: Date.now()
        };
        
        // Cache for 7 days
        this.cache.set(cacheKey, result);
        
        return { ok: true, ...result, fromCache: false };
    }
    
    return { ok: false, errorMessage: 'API call failed' };
}

Color Coding: Orange

Local transport segments are displayed in orange:

// Flutter route visualization
if (leg.mode == 'local') {
  return Container(
    decoration: BoxDecoration(
      border: Border.all(color: Colors.orange, width: 3),
      borderRadius: BorderRadius.circular(8),
    ),
    child: ListTile(
      leading: Icon(Icons.local_taxi, color: Colors.orange),
      title: Text('CNG/Rickshaw'),
      subtitle: Text('${leg.durationMin} min • ${leg.cost} BDT'),
    ),
  );
}

🚶 Walking

Overview

Walking is used for very short distances between nearby locations.

Walking Characteristics

Cost

Free

Walking costs nothing

Speed

~4-5 km/h

Average walking speed (Google Maps standard)

Range

< 1 km

Only suggested for very short distances

Comfort

Weather-dependent

Not ideal during rain or extreme heat

Use Cases

Between nearby stops: SUBIDBAZAR ↔ RIKABI_BAZAR (300m)
Campus navigation: Building to building
Last 100 meters: From bus stop to exact destination

Data Model

{
  "from": "SUBIDBAZAR",
  "to": "RIKABI_BAZAR",
  "mode": "walk",
  "time_min": 4,
  "distance_meters": 300,
  "cost": 0,
  "one_way": false
}

Color Coding: Green

Walking segments are displayed in green:

if (leg.mode == 'walk') {
  return Container(
    decoration: BoxDecoration(
      border: Border.all(color: Colors.green, width: 3),
      borderRadius: BorderRadius.circular(8),
    ),
    child: ListTile(
      leading: Icon(Icons.directions_walk, color: Colors.green),
      title: Text('Walking'),
      subtitle: Text('${leg.durationMin} min • ${leg.distanceMeters}m'),
    ),
  );
}

MND’s power lies in combining transport modes intelligently:

Example 1: Bus + Local

Route Breakdown:

Board Bus 1 at TILAGOR

Departure: 08:25 | Cost: 0 BDT

Ride bus for 30 minutes

Pass through: SHIBGONJ, NAIORPUL, KUMARPARA, SHAHI_EIDGAH

Drop off at AMBARKHANA

Arrival: 08:55

Take CNG to final destination

AMBARKHANA → LAKKATURA (10 min, 30 BDT)

Total: 40 min | 30 BDT

Example 2: Bus + Walk + Bus (Transfer)

Route Breakdown:

Board Bus 3 at NAIORPUL

08:30 departure

Ride to SUBIDBAZAR (20 min)

Free bus segment

Walk to RIKABI_BAZAR (5 min)

Short 400m walk between stops

Board Bus 6 at RIKABI_BAZAR

09:00 departure (5 min wait)

Arrive at CAMPUS (15 min)

Total journey: 40 min

Total: 40 min | 0 BDT

Example 3: Local Only (Fallback)

When Used:

❌ No bus routes serve both locations
⏰ Late night (no buses running)
🚨 Emergency (can’t wait for bus)

Mode Selection Logic

How does MND decide which transport mode to use?

Decision Tree

Optimization Criteria

Fastest Route
Least Local
Weighted Score

Minimize total journey time including:

⏰ Wait time for bus
🚌 Bus travel time
🚕 Local transport time
🚶 Walking time

Formula:

totalTimeMin = waitTime + busTravelTime + localTravelTime + walkTime

Minimize paid transport time:

✅ Prefer free bus routes
✅ Accept longer total time if it reduces cost
✅ Maximize bus coverage

Formula:

localTimeMin = sum(leg.durationMin where leg.mode == 'local')

For Bus + Local strategy, apply penalty to local transport:

const LOCAL_PENALTY = 1.5;
const score = waitTime + busTravelTime + (localTime * LOCAL_PENALTY);

This ensures the algorithm favors bus travel over local transport, even if slightly slower.

Transport Mode Statistics

Network Coverage

Bus Edges

1,537 connections50% of total graph edges

Local Edges

1,200 connections39% of total graph edges

Walking Edges

337 connections11% of total graph edges

Average Journey Composition

Morning Commute
Afternoon Return
Off-Hours

07:00 - 10:00 (to campus)

Mode	% of Routes	Avg Time	Avg Cost
Bus Only	45%	40 min	0 BDT
Bus + Local	35%	35 min	25 BDT
Local Only	20%	25 min	60 BDT

Mode	% of Routes	Avg Time	Avg Cost
Bus Only	50%	35 min	0 BDT
Bus + Local	30%	30 min	20 BDT
Local Only	20%	20 min	50 BDT

Mode	% of Routes	Avg Time	Avg Cost
Local Only	100%	25 min	70 BDT

Visual Reference

Transport Mode Icons

Bus

🚌 Blue routesFree scheduled service

CNG

🚕 Orange routesPaid on-demand

Walking

🚶 Green routesFree pedestrian

Route Card Design (Flutter)

// From mnd_flutter/lib/widgets/route_card.dart
Widget buildRouteLeg(RouteLeg leg) {
  final modeConfig = {
    'bus': {
      'icon': Icons.directions_bus,
      'color': Colors.blue,
      'label': 'Bus ${leg.routeId?.toUpperCase()}'
    },
    'local': {
      'icon': Icons.local_taxi,
      'color': Colors.orange,
      'label': 'CNG/Rickshaw'
    },
    'walk': {
      'icon': Icons.directions_walk,
      'color': Colors.green,
      'label': 'Walking'
    },
  }[leg.mode]!;
  
  return Container(
    padding: EdgeInsets.all(12),
    decoration: BoxDecoration(
      border: Border.all(color: modeConfig['color'], width: 3),
      borderRadius: BorderRadius.circular(8),
    ),
    child: Row(
      children: [
        Icon(modeConfig['icon'], color: modeConfig['color'], size: 32),
        SizedBox(width: 12),
        Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(modeConfig['label'], style: TextStyle(fontWeight: FontWeight.bold)),
            Text('${leg.from} → ${leg.to}'),
            Text('${leg.durationMin} min • ${leg.cost} BDT'),
          ],
        ),
      ],
    ),
  );
}

API Response Example

Here’s how transport modes appear in API responses:

{
  "from": "NAIORPUL",
  "to": "LAKKATURA",
  "requestTime": "08:30",
  "options": [
    {
      "label": "Fastest Route",
      "category": "fastest",
      "totalTimeMin": 45,
      "totalCost": 30,
      "legs": [
        {
          "mode": "bus",
          "route_id": "bus3",
          "from": "NAIORPUL",
          "to": "AMBARKHANA",
          "departure": "08:30",
          "arrival": "09:00",
          "durationMin": 30,
          "cost": 0,
          "source": "graph"
        },
        {
          "mode": "local",
          "submode": "driving",
          "from": "AMBARKHANA",
          "to": "LAKKATURA",
          "durationMin": 15,
          "distanceMeters": 2500,
          "cost": 30,
          "source": "distance_matrix"
        }
      ]
    }
  ]
}

Next Steps

Graph Model

See how transport modes connect 19 locations

Routing Algorithm

Learn how modes are combined optimally

API: Plan Route

Try the routing API with different modes

Architecture

Understand the full system design

Get Started

Core Concepts

User Guides

Documentation Index

​Overview

Bus

Local

Walking

​🚌 Bus Transport

​Overview

​Data Model

​Travel Time Calculation

​Color Coding: Blue

​🚕 Local Transport (CNG/Rickshaw)

​Overview

​Data Model

​Cost Calculation

​Distance Matrix Integration

​Color Coding: Orange

​🚶 Walking

​Overview

​Data Model

​Color Coding: Green

​Multi-Modal Routes

​Example 1: Bus + Local

​Example 2: Bus + Walk + Bus (Transfer)

​Example 3: Local Only (Fallback)

​Mode Selection Logic

​Decision Tree

​Optimization Criteria

​Transport Mode Statistics

​Network Coverage

Bus Edges

Local Edges

Walking Edges

​Average Journey Composition

​Visual Reference

​Transport Mode Icons

Bus

CNG

Walking

​Route Card Design (Flutter)

​API Response Example

​Next Steps

Graph Model

Routing Algorithm

API: Plan Route

Architecture

Build docs developers (and LLMs) love

Overview

🚌 Bus Transport

Overview

Data Model

Travel Time Calculation

Color Coding: Blue

🚕 Local Transport (CNG/Rickshaw)

Overview

Data Model

Cost Calculation

Distance Matrix Integration

Color Coding: Orange

🚶 Walking

Overview

Data Model

Color Coding: Green

Multi-Modal Routes

Example 1: Bus + Local

Example 2: Bus + Walk + Bus (Transfer)

Example 3: Local Only (Fallback)

Mode Selection Logic

Decision Tree

Optimization Criteria

Transport Mode Statistics

Network Coverage

Average Journey Composition

Visual Reference

Transport Mode Icons

Route Card Design (Flutter)

API Response Example

Next Steps