if you want to change the value with the new one, you can use:

ON DUPLICATE KEY UPDATE 
    doctets = VALUES(doctets) ;

or if you want to add the new value to the existing one:

ON DUPLICATE KEY UPDATE 
    doctets = doctets + VALUES(doctets) ;

Let's say you made the table like this

CREATE TABLE TrainEvents
(
    id INT NOT NULL AUTO_INCREMENT,
    station_arr_id INT NOT NULL,
    station_dep_id INT NOT NULL,
    arr_dt DATETIME NOT NULL,
    dep_dt DATETIME NOT NULL,

    ...
    PRIMARY KEY (id),
    KEY station_arr_index (station_arr_id,arr_dt),
    KEY station_dep_index (station_dep_id,dep_dt)
);

Next, you insert into the table the event

• Arriving From Station 21 on April 30, 2014
• Arrived at Station 29 at 10:00 AM on April 30, 2014
• Departing From Station 29 1 minute later

Here is that INSERT query

INSERT INTO TrainEvents (station_arr_id,arr_dt,station_dep_id,dep_dt)
VALUES (21,'2014-04-30 10:00:00',29,'2014-04-30 10:01:00');

OK, now let's see how you can query the following departure

• All Departures 10:00 AM on April 30, 2014 from Station 29
• Check Departures 15 minutes before and after

Here is that SELECT query

SET @MinuteWindow = 15;
SET @DepartureDT = '2014-04-30 10:00:00';
SET @DepartureDTMinBef = @DepartureDT - INTERVAL @MinuteWindow MINUTE;
SET @DepartureDTMinAft = @DepartureDT + INTERVAL @MinuteWindow MINUTE;
SELECT * FROM TrainEvents
WHERE station_dep_id = 29
AND dep_dt >= @DepartureDTMinBef;
AND dep_dt <= @DepartureDTMinAft;

EPILOGUE

Given your initial idea, you could change the station_arr_id and station_dep_id into a single route_id and store the routes in a route table

CREATE TABLE TrainRoutes
(
    station_id INT NOT NULL AUTO_INCREMENT,
    station_name VARCHAR(128) NOT NULL,

    ...
    PRIMARY KEY (station_id),
    KEY station_name_ndx (station_name)
);
CREATE TABLE TrainEvents
(
    id INT NOT NULL AUTO_INCREMENT,
    route_id INT NOT NULL,
    arr_dt DATETIME NOT NULL,
    dep_dt DATETIME NOT NULL,

    ...
    PRIMARY KEY (id),
    KEY arr_index (route_id,arr_dt),
    KEY dep_index (route_id,dep_dt)
);

You could also make the event record arrivals and departures separately.

CREATE TABLE TrainRoutes
(
    station_id INT NOT NULL AUTO_INCREMENT,
    station_name VARCHAR(128) NOT NULL,

    ...
    PRIMARY KEY (station_id),
    KEY station_name_ndx (station_name)
);
CREATE TABLE TrainEvents
(
    id INT NOT NULL AUTO_INCREMENT,
    route_id INT NOT NULL,
    event_dt DATETIME NOT NULL,
    event_type TINYINT NOT NULL # 1 for arrival, 2 for departure

    ...
    PRIMARY KEY (id),
    KEY event_index1 (route_id,event_dt,event_type),
    KEY event_index2 (route_id,event_type,event_dt),
);

I am just giving ideas. I'll leave it to you to implement. Perhaps, to give you some UI ideas, see the site I use to commute : http://as0.mta.info/mnr/schedules/sched_form.cfm . The result of the route you pick in that site shows route departures within a 5-hour window (2.5 hours before and 2.5 hours after).

Give it a Try !!!