code: public double transitionLogProbability(double routeLength, double linearDistance) {
          // Transition metric taken from Newson & Krumm.
          Double transitionMetric = Math.abs(linearDistance - routeLength);
  
          return Distributions.logExponentialDistribution(beta, transitionMetric);
      }
docs: Returns the logarithmic transition probability density for the given
  transition parameters.
  
  @param routeLength    Length of the shortest route [m] between two
  consecutive map matching candidates.
  @param linearDistance Linear distance [m] between two consecutive GPS
  measurements.