Laravel conditional response from Model - laravel

Question

I have three tables locations, unique_routes and tours, migration example is below.
// locations table
public function up() {
Schema::create('locations', function (Blueprint $table) {
$table->increments('id');
$table->string('name')->unique();
// extra data ...
});
}
// unique_routes table
public function up() {
Schema::create('unique_routes', function (Blueprint $table) {
$table->increments('id');
$table->integer('location_id_1')->unsigned();
$table->integer('location_id_2')->unsigned();
// extra data ...
});
Schema::table('unique_routes', function (Blueprint $table) {
$table->foreign('location_id_1')->references('id')->on('locations')->onDelete('cascade');
$table->foreign('location_id_2')->references('id')->on('locations')->onDelete('cascade');
});
}
// tours table
public function up() {
Schema::create( 'tours', function ( Blueprint $table ) {
$table->increments( 'id' );
// extra data ...
$table->integer( 'unique_route_id' )->unsigned();
$table->boolean( 'reverse_route' )->default( 0 );
// extra data ...
} );
Schema::table( 'tours', function ( Blueprint $table ) {
$table->foreign( 'unique_route_id' )->references( 'id' )->on( 'unique_routes' );
} );
}
And Models:
class Tour extends Model {
public function unique_route() {
return $this->belongsTo( Route::class, 'route_id', 'id' );
}
}
class UniqueRoute extends Model {
public function location_one() {
return $this->belongsTo('App\Location', 'location_id_1', 'id');
}
public function location_two() {
return $this->belongsTo('App\Location', 'location_id_2', 'id');
}
}
If I need location one name from unique route from tour:
$tour->route->location_one->name
It works OK.
The problem is that sometimes I need location_two object if "reverse_route" on tours is true! The question that I have is, how can I set conditional on Model? Or is there another approach?