Program: 189492
Project: 189492
Buggy source:
/** 
 * <b>Attention</b>: When we're projected onto a vertex of the LineString then we can have multiple transformations. <br> More importantly, we can lose velocity by performing this projection (how much dependents on the orientation of the edge(s) being we're projecting onto)! However, we can preserve it by simply using the velocity projection's direction and the velocity magnitude of the original 4D vector. This must be done by the user with the results of this method. <br> <br> The returned projection is always in the positive direction.
 * @param locVelocity
 * @param path
 * @param pathEdge
 * @return
 */
public static PathEdgeProjection getRoadProjection(Vector locVelocity,Geometry pathGeometry,boolean pathIsBackwards,Geometry edgeGeometry,double edgeDistanceToStartOnPath){
  Preconditions.checkArgument(locVelocity.getDimensionality() == 2 || locVelocity.getDimensionality() == 4);
  Preconditions.checkArgument(edgeGeometry == null || pathGeometry.contains(edgeGeometry));
  if (locVelocity.getDimensionality() == 2)   return null;
  final Vector m=locVelocity.clone();
  final LinearLocation lineLocation;
  final Coordinate currentPos=GeoUtils.makeCoordinate(AbstractRoadTrackingFilter.getOg().times(m));
  final double distanceToStartOfSegmentOnGeometry;
  final LineSegment pathLineSegment;
  if (edgeGeometry != null) {
    final Geometry edgeGeom=edgeGeometry;
    final LocationIndexedLine locIndex=new LocationIndexedLine(edgeGeom);
    final LinearLocation tmpLocation=locIndex.project(currentPos);
    final LengthIndexedLine tmpLengthIdx=new LengthIndexedLine(edgeGeom);
    final double lengthOnEdge=tmpLengthIdx.indexOf(tmpLocation.getCoordinate(edgeGeom));
    pathLineSegment=tmpLocation.getSegment(edgeGeom);
    final LengthIndexedLine lengthIndex=new LengthIndexedLine(edgeGeom);
    distanceToStartOfSegmentOnGeometry=Math.abs(edgeDistanceToStartOnPath) + lengthIndex.indexOf(pathLineSegment.p0);
    lineLocation=LengthLocationMap.getLocation(pathGeometry,Math.abs(edgeDistanceToStartOnPath) + lengthOnEdge);
  }
 else {
    final LocationIndexedLine locIndex=new LocationIndexedLine(pathGeometry);
    lineLocation=locIndex.project(currentPos);
    pathLineSegment=lineLocation.getSegment(pathGeometry);
    final LengthIndexedLine lengthIndex=new LengthIndexedLine(pathGeometry);
    distanceToStartOfSegmentOnGeometry=lengthIndex.indexOf(pathLineSegment.p0);
  }
  return PathUtils.posVelProjectionPair(pathLineSegment,distanceToStartOfSegmentOnGeometry);
}

Fixed version (ground truth):
/** 
 * <b>Attention</b>: When we're projected onto a vertex of the LineString then we can have multiple transformations. <br> More importantly, we can lose velocity by performing this projection (how much dependents on the orientation of the edge(s) being we're projecting onto)! However, we can preserve it by simply using the velocity projection's direction and the velocity magnitude of the original 4D vector. This must be done by the user with the results of this method. <br> <br> The returned projection is always in the positive direction.
 * @param locVelocity
 * @param path
 * @param pathEdge
 * @return
 */
public static PathEdgeProjection getRoadProjection(Vector locVelocity,Geometry pathGeometry,boolean pathIsBackwards,Geometry edgeGeometry,double edgeDistanceToStartOnPath){
  Preconditions.checkArgument(locVelocity.getDimensionality() == 2 || locVelocity.getDimensionality() == 4);
  if (locVelocity.getDimensionality() == 2)   return null;
  final Vector m=locVelocity.clone();
  final LinearLocation lineLocation;
  final Coordinate currentPos=GeoUtils.makeCoordinate(AbstractRoadTrackingFilter.getOg().times(m));
  final double distanceToStartOfSegmentOnGeometry;
  final LineSegment pathLineSegment;
  if (edgeGeometry != null) {
    final Geometry edgeGeom=edgeGeometry;
    final LocationIndexedLine locIndex=new LocationIndexedLine(edgeGeom);
    final LinearLocation tmpLocation=locIndex.project(currentPos);
    final LengthIndexedLine tmpLengthIdx=new LengthIndexedLine(edgeGeom);
    final double lengthOnEdge=tmpLengthIdx.indexOf(tmpLocation.getCoordinate(edgeGeom));
    pathLineSegment=tmpLocation.getSegment(edgeGeom);
    final LengthIndexedLine lengthIndex=new LengthIndexedLine(edgeGeom);
    distanceToStartOfSegmentOnGeometry=Math.abs(edgeDistanceToStartOnPath) + lengthIndex.indexOf(pathLineSegment.p0);
    lineLocation=LengthLocationMap.getLocation(pathGeometry,Math.abs(edgeDistanceToStartOnPath) + lengthOnEdge);
  }
 else {
    final LocationIndexedLine locIndex=new LocationIndexedLine(pathGeometry);
    lineLocation=locIndex.project(currentPos);
    pathLineSegment=lineLocation.getSegment(pathGeometry);
    final LengthIndexedLine lengthIndex=new LengthIndexedLine(pathGeometry);
    distanceToStartOfSegmentOnGeometry=lengthIndex.indexOf(pathLineSegment.p0);
  }
  return PathUtils.posVelProjectionPair(pathLineSegment,distanceToStartOfSegmentOnGeometry);
}