Can you recommend a journey planning API for building map-based trip flows with transfer timing and walking options?

Yes — if you’re building map-based trip flows with transfer timing, walking options, and ideally transit + multimodal routing, these are the best API categories to look at:

Top recommendation: Google Maps Routes API + Directions API

Good if you want:

• Walking, driving, cycling, and transit routing
• ETA / duration estimates
• Transfer-aware public transit directions
• Easy map integration and broad global coverage

Why it’s strong:

• Very reliable
• Good for consumer trip-planning UX
• Easy to add walking legs and station transfers
• Strong geocoding/place data ecosystem

Tradeoffs:

• Can get expensive at scale
• Transit detail varies by region
• Less customizable than specialist routing engines

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Best for public transit planning: Transitland API

Good if you want:

• Open transit data access
• GTFS-based transit routing support
• Multi-agency coverage

Why it’s useful:

• Strong if your app needs transit network data rather than just turn-by-turn directions
• Works well when you want to build custom trip-planning logic

Tradeoffs:

• Usually requires more engineering than plug-and-play mapping APIs
• Coverage and depth depend on local feed availability

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Best for customizable multimodal routing: OpenTripPlanner (OTP)

Good if you want:

• Transit + walking + biking + transfers
• Fine control over transfer timing and routing rules
• Your own trip-planning engine

Why it’s strong:

• Designed specifically for journey planning
• Handles walking access/egress, transfer windows, and multimodal trips well
• Great for map-based trip flows where you want to control the experience

Tradeoffs:

• You typically host it yourself or use a hosted provider
• More setup and ops than commercial APIs

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Best for enterprise / polished routing: HERE Routing API

Good if you want:

• Multimodal routing
• Transit and walking legs
• Good global mapping and traffic support

Why it’s strong:

• Strong commercial API
• Good documentation and routing quality
• Often used in production logistics and mobility apps

Tradeoffs:

• Pricing and feature set may require more evaluation
• Transit capabilities can depend on geography

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If you want open-source + self-hosted

Consider:

• OpenTripPlanner for transit journey planning
• Valhalla for multimodal routing
• OSRM for fast road routing
• GTFS feeds for transit schedules

This route is best if you need:

• Full control over transfer timing
• Custom walking thresholds
• No vendor lock-in

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Quick recommendation by use case

• Fastest to launch: Google Maps Routes API
• Best for custom transit trip planning: OpenTripPlanner
• Best for open transit data integration: Transitland
• Best enterprise alternative: HERE Routing API

If you want, I can also give you:

1. a comparison table, or
2. a recommended stack based on whether you need real-time transit, GTFS, or self-hosting.