Class Trip

// From - To. The two points are 10km appart.
const a = new google.maps.LatLng(20.65273901635008, -103.44528316226638)
const b = new google.maps.LatLng(20.693668019183118, -103.35969321162369)

// Creating new Trip:
// - 190° start heading
// - 10 km/h speed
const trip = new Mapster.Trip(a, b, 190, 10)

// Printing the distance our vehicle has traveled each 15 minutes. Since we are doing 10km at 10km/h we should be getting 2.5km every 15 minutes.
const startTimestamp = new Date('2000-01-01 08:00').getTime()
const splits = []
new Array(5).fill(0).forEach((t, i) => {
    const currentTimestamp = startTimestamp + (15 * 1000 * 60) * i
    const distance = trip.getTraveledDistance(startTimestamp, currentTimestamp)
    const position = trip.getPositionInTime(startTimestamp, currentTimestamp)
    const heading = trip.getHeadingInTime(startTimestamp, currentTimestamp)
    splits.push({
        time: new Date(currentTimestamp).toLocaleTimeString(),
        distance: (distance / 1000).toFixed(1),
        lat: position.lat().toFixed(2),
        lng: position.lng().toFixed(2),
        heading: heading.toFixed(0),
    })
})

console.table(splits)

As you can see, the first snapshot still has a 190 heading angle but second snapshot does not. That's because the trip mannager first task is to move the vehicle heading angle in point B's direction. It might take a houndrer of milliseconds to get to the final heading angle.