def computeInterGreen(perceptionReactionTime, initialSpeed,
    intersectionLength, vehicleAverageLength=6, deceleration=3):
    """Computes the intergreen time (yellow/amber plus all red time)
    Deceleration is positive
    All variables should be in the same units"""
    if deceleration > 0:
        return [perceptionReactionTime + float(initialSpeed) / (2 *
            deceleration), float(intersectionLength + vehicleAverageLength) /
            initialSpeed]
    else:
        print('Issue deceleration should be strictly positive')
        return None
