Question:
Kindly assist me with the following scenario.
We have a property with a double carrage way running up and down our site. We have cars and busses travelling on this road however it is too narrow accommodating a car and a bus at the same time. I want to suggest a lay-by lane staggered on either side of the road but need the correct terminology when addressing the client. Does the bus have right of way on the narrow road?
Looking forward to your response.
Answer:
12.2.8 Chicane – Pinch Points/Chokers
It is generally called a chicane, pinchpoint or a choker.
I copy the relevant section from Vol 2 of the SADC Road Signs Manual for you.
1 A chicane is formed by developing two adjacently located pinch points/chokers on opposite sides of the road. These measures reduce the carriageway width at either one location, or two adjacent locations on opposite sides of the road. The width reduction can vary to allow two cars to pass each other slowly, but where it would be difficult for a car and a bus or heavy vehicle to pass “comfortably”. The most common form allows for the passage of one vehicle, in one direction only, at a time.
12.4.6 Chicanes or Pinch Points
1 Typical traffic calming signing layouts for a chicane are shown in Figure 12.8. Other aspects with respect to the implementation of chicanes/pinch points are outlined below.
2 Pinch points reduce the carriageway width on opposite sides at a specific part of the road. It is also possible to have a single pinch point on one side of the carriageway (see Detail 12.8.3). A useful width restriction is to allow for a carriageway width where two cars can pass each other slowly (carriageway width 4.2 m to 4.4 m) but one car and a bus or heavy goods vehicle together would have difficulties in passing. More commonly used are pinch points that only one vehicle can negotiate at a time (carriageway width 2.75 m to 3.2 m).
3 The form and shapes of pinch points vary considerably. Often they are constructed as pavement peninsulas or as small planted areas combined with trees. This type of pinch point may be designed in such a way that the existing road drainage is unaffected. It is also possible to use pinch points in combination with cycle facilities. Such pinch points are used as separators between the carriageway and the cycle lane.
4 In order to maintain a low speed over a longer stretch of road, pinch points, for one-or two-way traffic, should be placed not more than 50 m apart (30 m to 40 m spacings are, in fact, advisable).
5 In regard to the suitability of pinch points for one-way and two-way traffic flows, the following should be noted:
(a) One-Way Traffic: pinch points reducing the carriageway to one lane are not suitable for main roads with high traffic flows. The Dutch traffic calming manual only recommends pinch points for flows of 400 to 600 vehicles per peak hour (maximum 4,000 to 6,000 vehicles per 12 hours); according to the Danish manual, pinch points that reduce the carriageway width to one lane are advised only for traffic flows of up to 3,000 motor vehicles per day.
(b) Two-Way Flow: pinch points reducing the carriageway width to 4.2 m to 4.4 m could be used on roads with higher motor vehicle flows than recommended in the Dutch manual, but only if the heavy goods vehicle and bus proportions are low (about 5% and less).
6 Pinch points with a high frequency of buses and/or HGV’s need a wider carriageway width (4.6 m to 4.8 m). The Dutch manual suggests a carriageway width for two-way traffic of 5 m to 6 m when there is a high portion of bus and heavy goods vehicle traffic. However, the speed-reducing effect will then be minimal unless other traffic calming measures are added.
7 Pinch points appear to be ideal for low-frequency bus routes when neither road humps nor speed cushions are acceptable to bus operators.
8 Pinch points need enough light to be seen well in advance by motor vehicle drivers during the hours of darkness. This will also apply for chicanes.
9 As with all traffic calming measures, chicanes and pinch points need to be complemented by traffic control devices of various sorts to ensure that drivers are made aware of the presence of the “obstruction” in their anticipated or normal path. The extent of this marking for visibility is likely to depend on whether the measures have been installed as part of an initial development, complete with landscaping, or as an after measure with little attention to landscaping. The least that is likely to be required is the use of retroreflective panels on decorative bollards placed on the chicanes or pinch points and the possible use of KERBFACE marking GM8.
10 For a one-way pinch point some form of control over the passage of vehicles in one direction is required. Depending on the geometry of the pinch point, AND whether if forms part of an intersection, conventional STOP signs R1 or YIELD signs R2 may be used. However, pinch points are commonly located in a mid-block position and the use of YIELD TO ONCOMING TRAFFIC sign R6 in one direction, and either RIGHT OF WAY sign IN7 or an appropriate DIAGRAMMATIC sign in the other direction. If sight distance to the pinch point is limited, advance versions of signs R6, IN7 or a DIAGRAMMATIC sign may be used with SUPPLEMENTARY PLATE signs IN11.3. A YIELD LINE marking shall be provided on the approach which loses priority (see Detail 12.8.3).
11 The signing of a chicane or double pinch point will vary according to whether it is intended to operate on a one-way or two-way basis. Detail 12.8.1 shows controlled use by means of YIELD TO ONCOMING TRAFFIC signs R6. In such a situation the operation involves a “first-come/first-served” approach, whereby the vehicle arriving at a yield line whilst another is within the chicane area, shall yield to that vehicle, and so on (keeping in mind that this form of traffic calming is only appropriate for low orders of traffic volume – see paragraph 12.4.6.5). If the chicane is to work in a two-way manner there is no yield control involved and warning of the restriction in width should be given by ROAD NARROWS advance warning signs W328, W329 or W330 or by advance warning WIDTH RESTRICTION sign W360 and TWO-WAY TRAFFIC sign W212 (see Detail 12.8.2). In all cases the option exists to indicate the distance to the pinch point using SUPPLEMENTARY PLATE signs IN11.3 or to provide the “warning” message in a high visibility or diagrammatic sign form.
