maintenance#

The use of special illuminated variable speed limit and overhead lane control signs to advise drivers of lane closures and associated reduced speed limits ahead on the motorway involves detailed planning involving complex traffic arrangements and liaison with motorway traffic management centre(s).

Planning will comprise a fully documented guidance scheme in accordance with the Queensland MUTCD Part 3 and QGTTM.

General principles applying to planned lane closures on motorways using integrated variable speed limits and overhead lane control signals at roadwork sites and for special events are set out in this section.

2.3.1General#

The spacing of variable speed limit and lane control signs varies according to the location of entrance and exit ramps. Further, the location of the work site may vary between the variable speed limit signs.

A number of typical arrangement figures have been developed to assist with the preparation of the Traffic Management Plans. Users should choose these drawings depending on the distance of the work site to the variable speed limit and lane control sign which is immediately upstream.

Figures are included in Section 2.5 of this chapter for work in one lane where the distance between the work sites and the immediate upstream variable speed limit and lane control sign is:

0–150 m
150–300 m
300–500 m
500–750 m (60 km/h work area).

Figures are provided in Section 2.5 of this chapter for work in two lanes where the distance between the work sites and the immediate upstream variable speed limit and lane control sign is:

0–150 m
150–300 m
300–500 m
500–750 m (60 km/h work area).

Figures are also provided in Section 2.5 for work on shoulder where the distance between the work sites and the immediate upstream variable speed limit and lane control sign is:

0–300 m
300–500 m
500–750 m.

These distances have been chosen based on the requirement of buffer speed limits in Table 5.5, Part 3 of the QGTTM; that is, a buffer zone in advance of a 40 km/h work site should be 150 m minimum length, and a buffer zone in advance of a 60 km/h work site should be between 300 m in length.

In addition, figures are included for typical entry ramp and exit ramp arrangements:

lane closed across an exit ramp
lane closed across an entrance ramp
variable speed limits at entrance ramp merge.

2.3.2Speed management#

Principle 1: Normal traffic control devices are required#

All traffic management and control devices normally associated with work sites are to remain. This includes devices such as truck mounted attenuators, delineation and static signage. One Exception exists for the buffer zone in advance of the work site; static buffer speed limits are not required as these signs will be displayed on the variable speed limit signs instead.

Principle 2: One static speed limit is required at the work site#

The work area speed limit (that is, the last speed limit sign before the work area) must be a static sign. Therefore, in the instance that the electronic signs fail, the critical speed limit will be displayed. A back up plan will need to be implemented in this case (refer to Section 2.4 of this chapter).

Principle 3: Variable speed limit signs within the work area#

All variable speed limit signs within the work area should be set to the speed limit of the work area.

Principle 4: Speed limit signs just prior to the work site#

Where one or more lanes are closed, delineation is specified in the Queensland MUTCD to close the lanes and vehicles need to merge into an open lane. These merging manoeuvres should occur at a maximum speed limit of 80 km/h.

Principle 5Buffer speed limits#

Speeds must be reduced in 20 km/h steps on the approach to a work site in accordance with the Queensland MUTCD even if they are displayed on variable speed limit signs. Minimum distances described in Table 5.5 of the QGTTM Part 3 apply. Note that due to the spacing of variable speed limit signs, the actual distances between variable speed limit signs may exceed the minimum distances. Note that (unless absolutely necessary), it is desirable to keep the buffer distances as close to the minimum as possible. This is likely to increase speed compliance. The first variable speed limit signs beyond the work site will normally display the appropriate default speed limit for the road continuing beyond the works; that is, the speed does not need to be increased in 20 km/hr steps.

Principle 6Static speed limit sign at the end of the work site#

Static speed limit signs (R4-1 type) are to be placed at the end of the work site to indicate the speed limit beyond the end of the work site and until the next variable speed limit signs are passed. The END ROADWORK (T2-16, T2-17) sign is used together with the static speed limit sign.

Principle 7Entrance ramps#

The variable speed limit on the entrance ramp should be the same as that on the mainline on approach to the entrance ramp merge. This will ensure that vehicles merge at the same speed.

Principle 8Side mounted variable speed limit sign#

Side mounted variable speed limit signs (that is, without overhead lane control signs) along the mainline are used in a similar manner to integrated variable speed limit and lane control signs. A typical arrangement is shown in Section 2.6 of this chapter, Figure 2.6(n).

2.3.3Lane control#

Principle 9Lane closure on VSL / LCS#

Lane closures shall not be implemented on the integrated VSL / LCS until the variable speed limits have been reduced for the temporary roadworks.

Principle 10Flashing red crosses and red crosses#

A continuously flashing red cross must be shown as the first lane control device. One flashing red cross is the minimum amount of lane control. Normally, the flashing red cross is followed by a continuous red cross at the next gantry. Refer to the figures in Section 2.6 of this chapter.

Principle 11White arrows#

A diagonally upwards white arrow (left or right) overhead lane control signal is used to indicate that an exit ramp from the motorway is open, where a lane closure extends past the exit ramp.

Principle 12Speed limits in conjunction with lane control#

At the introduction of lane control signs (flashing or continuous red cross); the speed limit shall be reduced to 80 km/hr (maximum). This reduced speed limit should assist merging. Where it is necessary to close two lanes with a separation between the taper for each lane closure, a similar staggered warning shall be provided to drivers on the integrated VSL / LCS.

At no time shall flashing red crosses be displayed in adjacent lanes, except where a parallel lane type merge is closed adjacent to a closed main motorway traffic lane.

Principle 13Closure of a central lane#

Consistent with normal roadworks signing practice, a central traffic lane should not be closed in isolation. An adjacent lane(s) should also be closed.

Principle 14Low flow conditions#

In low flow conditions, extra lanes may be closed to provide sufficient space for worker safety and the method of work. This may increase lateral clearance and allow a higher work zone speed, reducing delays to drivers. This should be done in accordance with QGTTM Part 3, including Table 5.5, however, the available trafficable lanes must be able to service the traffic capacity.

2.3.4Other#

Principle 15Variable message signs#

Where available, permanent variable message signs should be used to display a message about the road work: for example, ROAD WORK AHEAD / REDUCE SPEED; LEFT LANE CLOSED / MERGE RIGHT.