Friday, February 12, 2016

Quick Way to Know if you are in the Traffic Lanes

Sailing in Puget Sound or other areas with much ship traffic, a primary ongoing navigation concern is where we are relative to the VTS shipping lanes. It is a matter of safety, and a matter of the Navigation Rules. On smaller powerboats and when sailing, we have no rights in the lanes:

Rule 10 (j). A vessel of less than 20 meters in length or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane.
In fact, it is worse than "no rights."  Normal obligations of the give way vessel start out with "When two power-driven vessels are crossing so as to involve risk of collision..." Other obligations are worded as "stay clear of..."  But "do not impede" is much stronger. This is partly explained in

Rule 8 (f) (i) A vessel which, by any of these Rules, is required not to impede the passage or safe passage of another vessel shall, when required by the circumstances of the case, take early action to allow sufficient sea room for the safe passage of the other vessel.
The Admiralty Court has clarified this even further to explain that it means not just preventing risk of collision but preventing the development of risk of collision.  (The sometimes heard interpretation of this rule to mean I can do whatever I want so long as the ship does not have to alter course, is in a sense doubly wrong as it is even more lax than staying clear.)

Thus if you choose to cross the path of a ship in the traffic lanes you have to consider not just whether you have plenty of time to get by, but you have to consider what could happen that might make this go wrong. I can't find the reference for the moment, but in recent news a collision did occur with a ship and a powerboat whose engine stalled right in front of path of the ship. Considering the speed of a ship and their inability to stop, this crossing did not avoid development of risk. The stalled engine is thus no defense at all.

I have one vivid recollection from racing in the very region to be discussed in the video below. The situation was such that the wind in the area of the lanes, toward the middle of the Sound, was much favored over winds more inshore. So there was a big advantage to be gained the farther we could sail out toward the middle. We were on a tack headed out to the lanes as a ship came down the inbound lane from some distance off. The skipper's tactic was to tack out till right in line with the ship's path and then tack back, which would provide plenty of increasing separation as we sailed away from the path of the approaching ship. It was considered a safe tactic as we did not cross the path of the ship.

Unfortunately, as happens sometimes, during the hurried tack, the sheet got a knot in it on the tack, and when you tack and do not throw off, you heave to!  Thus we were dead in the water in direct line of the ship. The sheet had to be cut, which was in retrospect a small price for making a maneuver that was indeed indefensible.  We did not avoid a circumstance within the shipping lanes that could develop into the risk of collision.

Knowing where you are relative to the lanes is crucial in these waters, as is knowing the Rules about interacting with the lanes.

With a full nav station running an echart program with the lanes marked, you could in principle see where are you are relative to the lanes at all times. But with such systems you have to zoom in and out to see what you want, and you can in fact over zoom with a slipped mouse click and lose the picture at just the wrong time. Also to be precise about it, you would have to call up a tool to actually measure the distance from the lanes etc.  Nevertheless, when you have full navigation underway and working well, this is usually not an issue to know where you are relative to the lanes.

But short handed you might not have continuous view of the echart, or in a small boat with no built in electronics you need another tool, which is the subject at hand, and electronics is the best solution.  And I would venture that if you race routinely in the area of the shipping lanes, it could well pay to set up your phone or a tablet to supplement your routine nav info with this trick that keeps you instantly aware of where you are relative to the lanes. It is an easy double check on important information.

There is no practical piloting methods that will tell us this to the level of accuracy needed in the time frame needed. We might, and often do, try to get away with just knowing there are lanes present, and then guessing where they are when we do see a ship approaching and then try to maneuver based on that.  But that can be dangerous, as we do not really know where the ship is within the lanes,  and this approach is at least very inefficient. You could be going out of your way to avoid the traffic and not need to.  (Though off topic a bit, I should add that if your echarting included a good AIS display from your own receiver—not some Internet relay, which is dangerous—that would tell you if the ships are in the right place.)

Thus we have this easy trick to solve the problem of knowing precisely where we are relative to the lanes. It can be done on a phone or tablet, so even the smallest vessel can use it.  This method is particularly valuable to those who sail or paddle in the same area, as you can set it up once and then just turn it on the next time without any set up.

The trick is to set up a fake route (waypoint 1 to waypoint 2) marking the center of the separation zone and then just monitor the XTE to that fake route as we sail in the vicinity of the lanes. Below is an outline of the process, followed by a video illustration.



Step 1. Set up a route on the echart along the center of the separation zone between the inbound and outbound lines. Lock and save the route.

Step 2. Measure the perpendicular distance from that route to the boundary of both the separation zone and the outer limit of the lane. In Puget Sound the lanes are about 0.5 nmi across with about 0.25 miles of separation zone between them. Thus the outer distance is 0.62 nmi and the inner distance is 0.12.

Step 3. Activate  the route as if you were sailing toward one of the end points. This is not the case, so distance and time to the waypoint, and so on will be nonsense (just don't display these), but the cross track error (XTE) will still be right. That display then tells you precisely were you are.  The COG and SOG, total time and distance sailed will be right, so these could be useful displays as well, but for this exercise it is the XTE we are focusing on.

XTE > 0.62 you are outside of the lanes

XTE < 06.2 you are inside the lane
XTE < 0.12 and you are in the separation zone.

The values and what they mean are the same on either side of the lanes, but the XTE display will change labels, such as R going to L, or >> going to <<, etc. The directions will depend on the order you have for the waypoints, but routes can always be reversed so that does not matter.



I will add here phone and tablet apps that work well for this as I find them. Here is one:
memory-map navigator, which has versions for iOS, Android, and Windows mobile. This is excellent inexpensive product, but I am sure there are others.








8 comments:

Captain Robert Reeder said...

This is an excellent trick, and can also be used with stand-alone GPS receivers which do not have charts integral to them. I've used this with a simple Garmin eTrex, with good results.

When boating in or near the VTS shipping lanes, it is also critical to monitor the VTS radio channels on VHS; this is where the commercial and military shipping will be communicating with the Coast Guard. In Puget Sound south of Bush Point this is VHS channel 14, north of Bush Point (or north of Possession Point if you are east of Whidbey Island) this is VHF channel 5a, and north of the international boundary Victoria VTS is VHF channel 11.

Note that commercial and military ships participating in the VTS system are NOT required to monitor VHF channel 16 or 9. They may be hailed on either the appropriate VTS channel, or else VHF channel 13.

Forrest said...

I keep a radio watch on 13 (commercial), as well... the combined vessel traffic authority and bridge-to-bridge communications can give you a good indication of situations that will develop, especially in areas with slow moving tug-and-tows that aren't necessarily operating inside the VTS.

Old Navy said...

US Navy ships (warships and Navy auxiliaries) monitor Channel 16 whether or not required by VTS. I can't speak for the civilian manned military subordinated vessels (the USNS ships, marked with a bands of blue and yellow on their stacks, are the ones most frequently encountered), having never served in them.

dbostrom said...

That is a slick trick, one of the best in the sense that it seems so blindingly obvious in hindsight. Routes can be left in plotter, ready to go. Nice.

Anonymous said...

"Rule 10 (j). A vessel of less than 20 meters in length or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane."
Does this rule apply to ANY "power-driven vessel following a traffic lane", or just to power-driven vessels >20 meters which are using the shipping lane?
Asked another way, if two boats each < 20 meters are in the shipping lanes, one is following the edge of the lane motoring north, and another crossing over the lane heading west (on the stb. side of the boat heading north), which rule applies? (Rule 10j or "boat to stb"?)
Finally, same boat <20 meters, motoring north following the traffic lane, but with a boat also < 20 meters under sail crossing the lane (heading east, and to the port side of the boat motoring). Which rule applies? (Rule 10j or sail over motor?)
There seems to be a lot of confusion about this situation in the Sound.
Thanks!

David Burch said...

There are two key references that answer your questions. First is the full set of Nav Rules, and we have a super convenient copy of the full new Nav Rules Handbook online at www.starpath.com/navrules/NavigationRulesHandbook.html

The next key document is the Puget Sound VTS Users Manual, which very specifically addresses points raised. see http://www.uscg.mil/d13/psvts/docs/userman032503.pdf

In Rule 10 (j) the statement “following a traffic lane” means a vessel in full participation in the VTS, which in practice are ships and tow boats, and other larger commercial vessels. The key part of their full participation is there scheduled radio contact with the VTS center, along with actually following the lanes. They are to be contrasted with vessels that just happen to be in the lanes at the moment, but later or earlier will take other routes that do not follow the lanes.

The vessels you refer to are not "following the lanes," they just happen to be in them at the moment.

The users guide explains who is required to have full participation and who may participate and under what conditions they may do so when not required.

20m is not required. >40m is. In practice, recreational vessels are expected to participate passively, as defined in the manual

so the fact that the track of the vessel is parallel to or inside or outside of the lane is not the key factor when interacting with a vessel clearly not required to follow

“Does this rule apply to ANY "power-driven vessel following a traffic lane", or just to power-driven vessels >20 meters which are using the shipping lane? “

So the answer to that is no. and again using the lane is not the issue, it is participating in the VTS which is here called following a lane.

Second part:

“Asked another way, if two boats each < 20 meters are in the shipping lanes, one is following the edge of the lane motoring north, and another crossing over the lane heading west (on the stb. side of the boat heading north), which rule applies? (Rule 10j or "boat to stb”?”

Assuming neither are “following the lanes” as described, these are just two vessels interacting in open water that has lanes defined there. then normal crossing rules or sail-power rules apply.

On the other hand, if there are indeed ships following the lanes, then both of these vessels must not impede them. non participating vessels are encouraged to use the inshore zones, not the lanes themselves.


Third part:
“Finally, same boat <20 meters, motoring north following the traffic lane, but with a boat also < 20 meters under sail crossing the lane (heading east, and to the port side of the boat motoring). Which rule applies? (Rule 10j or sail over motor?)”

I can see that there could be confusion about the wording, but i believe that once these points here are noted this should remove that confusion. In other words, if you are not in full participation with the VTS, which in almost all cases, you would not be doing unless you are a vessel required to, you gain no special rights when sailing in the lanes, regardless of your course. when you see other vessels not following the lanes in this sense, you interact as you would in open water, assuming there are no ships near by, as they then become “obstacles to your course.”

i hope that helps. You have brought up a good point here, and I will try to expand on this a bit and make a dedicated blog post on the topic.

Anonymous said...

Thank you very much for this clarification! Many times in crossing the shipping lanes in the Sound (while either under power or other times under sail) we have had power boats <20 meters not give way in situations where we clearly would have had the right of way if both of our boats were not in the shipping lane.
Two times years ago I tried to contact the Coast Guard for clarification and they were very vague about it, saying "just read the Rule- it says "power-driven vessel following a traffic lane" (but which does not include a clear definition). Your explanation makes sense.
It sure would help if the Rule was worded instead something like, "a power-driven vessel which is ACTIVELY PARTICIPATING in a traffic lane" (or REQUIRED TO PARTICIPATE...)
So thank you & I look forward to more posts on this matter.

David Burch said...

It could be the encounters you had in the lanes were with vessels that did not know the rules so they would have behaved same way no matter where they were.