User{id, name, phone, email}
Cars{id, name, manufacturer}
UserCars{id, car_id, user_id, role}

User have many cars(through UserCars)
Cars have many users(through UserCars)

router.get('/', async (req, res) => {

        try {

            let car = await Car.findOne({
                where: {
                id: req.car_id
            }});

            let users = await car.getUsers({joinTableAttributes: ['role']})
            res.send(users)

        } catch (e) {
            console.log(e)
            res.status(400).send(e)
        }

    })

[
    {
        "id": 1,
        "name": "test",
        "email": null,
        "phone": null,
        "createdAt": "2019-07-09T09:38:11.859Z",
        "updatedAt": "2019-07-12T04:34:20.922Z",
        "User_car": {
            "role": "driver"
        }
    }
]

[
    {
        "id": 1,
        "name": "test",
        "email": null,
        "phone": null,
        "role": 'driver'
        "createdAt": "2019-07-09T09:38:11.859Z",
        "updatedAt": "2019-07-12T04:34:20.922Z"
    }
]