Regulatory Sign/Filter in turn

The filter in turn sign is found exclusively in the Channel Islands (Guernsey and Jersey).

The history of the sign needs more investigating, at present it is not known by this wiki which island had the Filter concept first. However, the first Filter in Jersey specifically is the roundabout at Beaumont.

Meaning

The sign's meaning is defined by the Highway code and Traffic laws of each of the Bailiwicks.

The Jersey Highway Code Rule 172 intrdouces the filter as a prohibitive regulatory sign:

Filter in turn junctions. At an intersection marked by a filter in turn sign you MUST NOT enter any part of the carriageway into which you can see that another driver proposes to enter your path unless you; a) reach the intersection before that other driver, and b) the driver who last entered the intersection did not do so from the same entry as you. This means that in negotiating the junction you should TAKE YOUR TURN with other vehicles in joining or crossing any stream of traffic.

Although it is a MUST order, it is not clear which traffic law this is received from.

In the Jersey Traffic Signs Order, the previous iteration of the sign (simply black text on a white square background) is noted as traffic sign 828J, which somewhat bizarrely places it next to "Another Train Coming" in the 1975 UK TSRGD (presumably to reduce confusion, as that sign would not be found in Jersey with no railways. The sign is not prescibed any legal meaning, other than that emergency services can't be prosecuted for breaking that (lack of) meaning.

In the Guernsey Highway Code, the Filter in turn rule is explained in rule 32:

At a junction which is controlled by ‘Filter in Turn’ signs and road markings, all directions have equal priority, so you must Give way in turn to vehicles which also intend to enter the junction. Do not enter the box unless your exit is clear. TSTL

This ascribes a very slightly different legal meaning to the two junctions, however the intention and operation are largely the same.

Usage

Filter in turns are much more widely used. According to a survey done with Satellite imagery via QGIS, this author identified that Guernsey had 26 filter in turns (including one in the B&Q car park) and Jersey had 5 (also including one in the B&Q car park - not sure why B&Q seem to love filters).

The author also identified three broad types of filter in turn:

• Merge - this is the style most common to (some) UK drivers, as two separate lanes or roads come together and traffic must take it in turns (effectively the UK "Merge in turn"). This is the type most common in Jersey, e.g. at the Western end of the A2 and on the St Helier Ring Road at gyratory systems. Guernsey also uses it, especially in the town centre.
• Cross - this is where two streams of traffic cross, and must take it in turns, however the two dominant flows won't necessarily merge into the same flow. It is only found in Guernsey, the most prominent example being at 'the Bridge'.

Finally, there is the Hybrid mode. This is the one most common in Guernsey and most famous in Jersey. In Guernsey it normally appears in the form of a T-junction or crossroads with a yellow box, in Jersey it appears only as a roundabout, but without the give way to the right rule.