How do I make a simple bus route search Engine?

Question

[Not:e user is asking this again at Development of railway enquiry system, how to model Trains, Stations and Stops? ] My Problem Description:

Suppos

Answer 1

I'd model it as a cyclic graph. Each bus stop is represented by a vertice. Each direct connection between two stops is represented by an edge labelled with the route number; consequently, each route is a sequence of connected edges. Make the edges directed, too. Not all routes travelling from stop A to stop B will necessarily also travel from stop B to stop A in the other direction.

Probably want to populate each edge with the estimated travel time, a measure (or measures) of variance for that leg -- at 2am on a Sunday night, the variance might be low, but at 5pm on a Friday evening, it might be very high, and list of departure times as well.

Then its a matter of graph traversal and finding the "least cost" route, however you choose to define "least cost" -- Factors you might want to consider would include:

• Total travel time
• Total time spent waiting for the next leg to depart.
• Wait time at any individual stop.
• Distance?

One should note that too much wait time is bad (ever spend 40 minutes waiting for a bus in January when it's -10 F?). Too little is bad, too, as it increases the probability of missing a connection, given that buses tend to have a fairly large variability to their schedules since they are highly responsive to fluctuations in local traffic conditions.

That's how I would do it.

I don't believe I'd try to solve it directly in SQL, though.

The model is a good fit for SQL, though. You need the following entities, and then some, since you'll need to represent schedules, etc.:

• Stop. A Bus stop. The vertices of the graph.
• Route. A bus route.
• Segment. The direct link between two stops. The edges of the graph.
• RouteSegment. An associative entity representing ordered sequence of segments that composes the route.

Answer 2

I'd have a route table and a route_part table. The latter would contain a reference to the route, plus an ordinal number for sorting, and a reference to a stop table. Thus, you can store any route.

In terms of searching, if you wish to search for a route between two stops, you could look up the two stops in the route_part table and see if they appear on the same route in any cases (bearing in mind that a route may exist in one direction and not the other).

Answer 3

I think the bus_numbers aren't important because you can look them up later. Maybe what you need is to create a 2d matrix with the bus_stops in a big matrix having them all and then use a graph traversing algorithm like dijkstra to find the shortest path from A to B. When you got that you can easily lookup the bus_numbers and show them to the client. Thus I think your database is already very good.