Jaký druh vztahu vyžadují tyto 2 tabulky?

Hledáte spojovací/asociační tabulku. Tabulky by měly vypadat takto:

create table Journeys (
    Journey_Id int auto_increment primary key,
    Start_Station VARCHAR(50) NOT NULL,
    End_Station VARCHAR(50) NOT NULL,
    Start_Time VARCHAR(50) NOT NULL,
    End_Time VARCHAR(50) NOT NULL
)

create table TravelerJourneys (
    traveler_journey_id int auto_increment primary key,
    traveler_id int(6),
    journey_id int,
    foreign key (traveler_id) references travelers(National_ID_Number),
    foreign key (journey_id) references Journeys (journey_id)
);