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I built an interactive map to answer a practical question: “If I live here, where can I actually reach in under half an hour?” Choose or move an origin in Chittagong—also known as Chattogram—and the map shows car-travel areas for six time bands, from 10 to 60 minutes. You can view those areas as a polygon heatmap or as colored roads, then hover to see the smallest time band containing a point and, when available, a road name.
This is a walkthrough of the implementation I described, not an independently tested assessment of the live application. The stack summary names Next.js 15, while the closing line names Next.js 16; I leave the project’s exact major version unresolved rather than silently choosing one.
What the map shows
An isochrone is a boundary around an origin: points inside it are estimated to be reachable within a chosen travel-time threshold. Mapbox’s Isochrone API returns these reachable regions as GeoJSON contours that can be displayed as polygons or lines. The API supports driving, walking, and cycling profiles, with time contours capped at 60 minutes. Mapbox Isochrone API documentation
For this project, I focused on driving and used six thresholds: 10, 20, 30, 40, 50, and 60 minutes. The map offers two ways to read the result:
#1 Best Overall
- Bright, high-resolution 5” glass capacitive touchscreen display lets you easily view your route
- Get more situational awareness with alerts for school zones, speed changes, sharp curves and more
- View food, fuel and rest areas along your active route, and see upcoming cities and milestones
- View Tripadvisor traveler ratings for top-rated restaurants, hotels and attractions to help you make the most of road trips
- Directory of U.S. national parks simplifies navigation to entrances, visitor centers and landmarks within the parks
- Polygon heatmap: overlapping reachability areas make it easy to see how the reachable region expands with more time.
- Road coloring: roads are colored according to the time band that reaches them, making the output easier to interpret at street level.
These bands represent modeled travel-time reachability, not a promise about a particular trip’s actual duration. The project’s reported experience with local traffic and the Karnaphuli River is an implementation observation, not an independent citywide traffic measurement.
Why six time bands need two API requests
Mapbox allows a maximum of four contours in one Isochrone API request, and a request accepts one origin coordinate. Since this map uses six thresholds, I split them into two groups rather than trying to request all six at once. The API documentation also lists a limit of 300 requests per minute and request-based billing; results must be displayed on a Mapbox map using a Mapbox library or SDK. Check the current documentation and account terms when planning usage. Mapbox Isochrone API documentation
Rank #2
- 6” high-resolution navigator includes map updates of North America
- Hands-free calling when paired with your compatible smartphone with BLUETOOTH technology and convenient Garmin voice assist lets you ask for directions to places you want to go
- Road trip–ready features include the HISTORY database of notable sites, a U.S. national parks directory, Tripadvisor traveler ratings and millions of Foursquare POIs
- Driver alerts for things such as school zones, sharp curves and speed changes help encourage safer driving and increase situational awareness
- Access live traffic, fuel prices, parking, weather and smart notifications when you pair this navigator with your compatible smartphone running the Garmin Drive app
| Request | Contours in this project | Reason |
|---|---|---|
| 1 | 10, 20, 30, 40 minutes | Uses the four-contour per-request maximum. |
| 2 | 50, 60 minutes | Fetches the remaining bands within the same limit. |
In my implementation, the two requests run in parallel. I then combine their returned features for display. This is the author’s implementation description; it is not a claim about independently measured request latency.
How I organized the Next.js map
The stack summary in my project description lists Next.js App Router, Mapbox GL JS v3, Turf.js v7, TypeScript, and Tailwind CSS. Its closing line instead says Next.js 16, so the exact Next.js major version should be confirmed against the project before treating either figure as definitive.
Rank #3
- Explore confidently with the reliable handheld GPS
- 2.2” sunlight-readable color display with 240 x 320 display pixels for improved readability
- Preloaded with Topo Active maps with routable roads and trails for cycling and hiking
- Support for GPS and GLONASS satellite systems allows for tracking in more challenging environments than GPS alone
- 8 GB of internal memory for map downloads plus a micro SD card slot
Request and cache flow
When the origin changes, the app needs updated contours for that coordinate. My implementation description says it rounds longitude and latitude to four decimal places for a cache key, delays fetching by 300 milliseconds, and requests the two contour groups in parallel. The delay helps avoid launching a request for every small intermediate movement while dragging; the cache can reuse a response for a previously visited rounded coordinate.
- Read the origin: use the selected map coordinate as the center for the requested isochrones.
- Check the cache: look up the coordinate using longitude and latitude rounded to four decimal places, as described for this implementation.
- Wait for movement to settle: apply the reported 300 ms delay before fetching after a change.
- Fetch both contour groups: request 10–40 minutes and 50–60 minutes in parallel.
- Prepare the returned features: combine the results and sort by contour so larger polygons are drawn first, as described in the project walkthrough.
- Update the map: render the data in the selected polygon or road-coloring mode.
The rounding, delay, parallel requests, and drawing order are reported choices in the author’s implementation, not general Mapbox requirements or measured optimizations.
Rank #4
- 8” navigator with high-resolution, dual-orientation display and map updates of North America .Special Feature:Large Display; Voice Assist; Hands-Free Calling; Live Traffic and Weather; Traffic Cams and Parking; Smart Notifications,Driver Alerts; Tripadvisor; National Parks Directory; Find Places by Name; Garmin Real Directions Feature.
- Hands-free calling when paired with your compatible smartphone with BLUETOOTH technology and convenient Garmin voice assist lets you ask for directions to places you want to go
- Road trip–ready features include the HISTORY database of notable sites, a U.S. national parks directory, Tripadvisor traveler ratings and millions of Foursquare POIs
- Driver alerts for things such as school zones, sharp curves and speed changes help encourage safer driving and increase situational awareness
- Access live traffic, fuel prices, weather, parking and smart notifications when you pair this navigator with your compatible smartphone running the Garmin Drive app
Rendering polygons and roads
In polygon mode, the returned GeoJSON contours provide the areas for the time bands. Drawing larger polygons before smaller ones is the ordering approach described in the walkthrough; the intended effect is to keep smaller, more specific areas visible above broader ones. In road mode, the map colors road features according to their reachable time band.
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The author also reports encountering unwieldy large geometry expressions and describes a Tailwind styling workaround. Those are project-specific development experiences, not API guarantees. If a similar map becomes difficult to maintain, keep the contour data and its presentation logic separate enough that styling or rendering changes do not require rebuilding the routing request flow.
Best Value
- Bright, high-resolution 5” glass capacitive touchscreen display lets you easily view your route
- Get more situational awareness with alerts for school zones, speed changes, sharp curves and more
- View food, fuel and rest areas along your active route, and see upcoming cities and milestones
- View Tripadvisor traveler ratings for top-rated restaurants, hotels and attractions to help you make the most of road trips
- Directory of U.S. national parks simplifies navigation to entrances, visitor centers and landmarks within the parks
How the hover label is determined
For the hover interaction, I use Turf.js point-in-polygon testing to determine which time-band polygons contain the pointer’s map location. If several bands contain it, the label uses the smallest containing band—the tightest applicable reachability threshold. I also query Mapbox’s rendered features to look for a road label, so the tooltip can include a road name when one is available.
This describes the implementation approach, not an independently verified performance result. A tooltip can lack a road name when the rendered map does not provide one at the queried location; the time-band result and road-label lookup are separate pieces of information.
Using a browser-visible Mapbox token safely
A public Mapbox token is expected to be used in client-side applications, so it is not a secret in the same way as a server-only credential. That does not mean every token should be unrestricted. Mapbox recommends using only the necessary scopes and configuring URL restrictions where appropriate. Those restrictions are a best-effort mitigation, not a guarantee; requests from unauthorized origins can be rejected with a 403 response. Mapbox access-token guidance
- Use a public token intended for client-side use, with only the scopes the application needs.
- Configure URL restrictions for the sites that should use the token, where appropriate.
- Expect a 403 if an origin is not allowed by the configured restrictions, and check the restriction settings when diagnosing that failure.
What the map can—and cannot—tell you
The map is useful for comparing modeled reach from different origins and time thresholds. It does not establish a guaranteed door-to-door arrival time, and the six bands should not be read as a live traffic forecast unless the routing data and implementation explicitly support that interpretation. The project walkthrough reports an unexpected routing result near the Karnaphuli River, a reminder to inspect generated contours against the local geography rather than assuming every boundary will match a resident’s intuition.
Mapbox’s documented API limits establish the request shape and supported duration, but they do not independently establish how accurately a particular contour represents a specific Chittagong trip at a given time. Treat the output as a reachability visualization, and verify important journeys using current route information.
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