Single track road

A single track road, sometimes referred to as S1, is a single carriageway road which is only wide enough for a single lane of traffic to pass at a time. Passing places are usually provided to allow traffic to pass either in opposing directions or to overtake slower vehicles. Single track roads are found on routes with low volumes of traffic so are usually B, C or unclassified roads, but some A roads and trunk roads with low traffic volumes also have sections of single track, particularly in the North West Highlands. They are marked as such on Ordnance Survey mapping, where the symbol used is a dashed line, in place of the normal solid line, alternating between white and the colour of the classification. Since the completion of the A830 upgrade in 2009 there are no Primary single track roads in Scotland.

Definition

Single track roads can vary in width, although being less than two lanes wide, they can range from being barely wider than the vehicles travelling on them to being wide enough for narrower vehicles such as cars being able to pass each other, with only larger vehicles requiring passing places or using the verges to pass. Indeed, there are some very minor, and often dead-end routes, where the tarred width is insufficient for lorries, which can cause interesting situations with (for instance) Milk or Oil tankers trying to reach isolated farms. Some people have used terms such as WS1 and S1.5 to describe these wider roads, but it should be noted than none of these abbreviations relating to single track roads are official terminology or design standards.

Urban Routes

Of course, it is not just in rural areas where single track routes can be found. Many urban streets, particularly those that pre-date motor traffic in town and city centres, have a comparable width and traffic capacity and hence are nominally "S1". However, they are not usually considered to be single track roads. Old cities in particular, such as York, Lincoln or Durham have a number of very narrow streets, as do many of the small fishing villages along the Cornish coast, and elsewhere. Again, however, they are not officially single track, in the same sense that the rural routes are. This is down to a variety of reasons, partly due to the ability to use them as one-way streets in many case, and in others the volume of traffic is low enough, with widenings in the street to allow traffic to pass relatively unobstructed.

However, in a few cases, where there is no ability to widen or bypass them, without demolishing ancient and protected buildings, such narrow streets have become littered with road markings, signage and traffic lights to try and maintain a flow of traffic.

Single Track A Class Roads

The A830 near Mallaig was a partly single track road until 2009, and is marked as such on this OS map.

Whilst single track B Roads, and especially unclassified routes are still very common, most A roads are now full S2 routes. Most of the remaining single track A roads are in the Scottish Highlands and Islands, although the Highland Council have been working hard to eliminate many sections in recent years. The last major single track trunk road to be widened was the A830 between Fort William and Mallaig (the "Road to the Isles"), with the final section completed in 2009.

Below are those routes which still have lengthy single track sections, these lists are not complete:

• Scottish Highlands

A832, A836, A837, A838, A839, A861, A884, A890, A896, A897, A939, A8003

• Scottish Islands

A846 (Jura), A847, A848, A849, A855, A859, A865, A888, A970, A971

There are also some Scottish A roads, such as the A86, which do not have centre lines, but are in fact wide enough for two vehicles to pass, and so don't have passing places. These are narrow S2 routes, despite some drivers considering them to be single track.

• Wales A498, A4085

Outside Scotland, roads such as the A498 and A4085 through the northern section of Snowdonia National Park have similar markings and capacity to roads such as the A86. Other former S2 routes, such as the B4405 near Cadair Idris and Tal-y-Llyn have had a centre line removed to encourage traffic to slow down, though again it is possible for two vehicles to pass. These roads are not explicitly marked as single-track on Ordnance Survey mapping.

Passing Places

Passing place with current style sign

Most single track roads have passing places at regular intervals to allow traffic to pass either oncoming road users or to let slower vehicles allow faster traffic to overtake. Passing places usually consist of a widened part of the road on one side of the carriageway or the carriageway may widen on both sides.

The frequency of passing places can vary depending on the road, on more major single track roads passing places are usually close enough to be visible from one to the next allowing traffic to make steady progress past oncoming traffic. On minor and lowly trafficked routes passing places may be at sporadic intervals and can be some distance apart meaning traffic may have to reverse distances of several hundred meters to pass.

On some minor roads passing places may be unsurfaced other than gravel, although some have become completely grassed over due to lack of use, but in most cases they are constructed and surfaced to the same standard as the rest of the carriageway.

Use of passing places

Please note, the following is based on observations, and does not necessarily agree with the Highway Code.

The officially recommended means of using a passing place is to stop on your side of the road to let other traffic pass. Always stop so that there is sufficient room for the oncoming vehicle to enter the space safely. However, when encountering large vehicles, or long queues of oncoming traffic, it is often better to pull into a passing place, whichever side of the road it is on, to minimise the delay in passing.

When passing places are within sight of each other, it is best to try and meet at a place where neither vehicle needs to slow to any great extent, and so adjust your speed on approach accordingly. If you are following traffic you may need to stop in the previous place to ensure that all oncoming traffic can pass safely.

Diamond passing place sign

Sign advising drivers to allow faster traffic to pass

Location Signing

Passing places are usually marked with a sign to aid their visibility to drivers. The current design of passing place sign was introduced in the 1994 version of TSRGD is a white square with the text "passing place" in upper-case. The previous design of signs consisted of a white square at 45° from horizontal (often referred to as a diamond shape), also with the passing place text. This diamond sign is probably the most frequently seen passing place sign as most signs in place pre-date the change to the current design.

Older styles of passing place sign include plain white diamonds of various sizes or black and white striped poles with no sign plate. The passing place sign can be positioned either at the back of the passing place or on the opposite side of the carriageway.

More recently, rather than install two signs either side of a post, councils have reverted almost to the original single sign mounted on top of a pole. The latest design is a rectangular panel, printed double sided with a square 'passing place' sign, and the lower portion mounted to the top of the pole. The original passing place sign was a diamond with a flanged bracket at the base that sat over the top of the pole.

Advisory Signing

Other signs may be present on single track roads to advise drivers to use passing places to permit overtaking, these can take the form of worded information signs or diagrammatic versions, as seen on the right. A variety of wording is found, including those illustrated:

• Single track road
• Single track road With passing places
• Single track road Use passing places to permit overtaking - At least one example substituting facilitate for permit has been spotted in the past.
• Single track road Use passing places to allow overtaking - less common that the above sign.
• Please use passing places to permit overtaking
• Police Notice Use passing places to allow traffic behind to overtake
• Police Notice <diagram> Allow overtaking

The first sign can be used in advance of an S1 section of road, often in conjunction with the Road Narrows warning sign. However, all are more commonly used as reminders within a single track section of road.