Solution to Motorway Congestion

ISSUE 

Significant traffic congestion on the M1 and other national motorways is costing millions in lost productivity, driver injury and lives.

A ROOT CAUSE

1. Traffic is hindered by traffic flow oscillations also known as traffic waves that result in a section of the motorway coming to a complete stand still, while other sections are at speed.

2. Three elements that cause traffic waves:

a) Driver decision making: not achieving a clear vision of 12 secs for decision processes, such as sharper crests and curves, e.g. through Tanah Merah to Springwood section of the M1 in Queensland;

b) Driver attitude: slower/timid drivers in the uncontrolled flow with aggressive accelerating drivers;

c) Traffic actions: merging traffic including onto the motorway and lane changing to gain a perceived advantage in road position.

TRAFFIC WAVES

When traffic has an unhindered path of travel, for example, no accidents, incidents, roadworks or debris on the road, there is another cause for vehicles to come to a complete stop on motorways. This reason is known as traffic oscillation and commonly known as traffic waves or a shock wave. 

Traffic waves are caused by several contributing factors based on a root cause of when cars travel faster than the car in front, and then initiate either a hesitation or braking to re-match speed, subsequent following cars then react, each greater than the car in front. This results in the car that causes the hesitation remains at speed and cars 6 – 20 back in the flow, coming to a complete stop, a shockwave.

Contributing factors

1.   Loss of forward scanning: When drivers hesitate as a result of losing 12 secs of clear vision of the road and the associated hazards ahead. This includes when a motorway has a sharper curve/crest in the road, such as through Springwood and along the section Gaza Road to Stanley Street exits in Queensland. Drivers create this 12 secs by slowing to facilitate decision making. Concerns include expectation of stopped traffic ahead from traffic waves, and the other contributing factors explored below.

2.   Insufficient following distance: This is created by vehicles not having 2-3 seconds of safety space between vehicles. This reduction in safety space is generated primarily from driver attitude to the following point, merging drivers. When vehicles ‘tail gate’ or follow too closely, they are not able to absorb small changes in the speed of vehicles in front.

3.   Merging vehicles: When vehicles merge between lanes, they immediately significantly reduce the safety space between ‘at speed’ traffic, causing vehicles behind to wash speed off, often breaking, including harsh breaking. Driver attitude facilitates this factor, by setting a close following distance to eliminate merging, in particular, to prevent lane changing solely for the purpose of attempting to gain an advantage in road position, which is ‘not for exiting purposes’. This is magnified at entrance points to the motorway.

CHANGE IN PRINCIPLE:

The current Queensland Traffic and Road Use Manual (TRUM) sets a principle that unless otherwise deemed, drivers may change lanes at any time, hence the extensive use of the dotted line dividing lanes. This principle needs to change on the M1 Motorway and other like corridors. 

The new principle needs to be that drivers may change lanes when it is safe to do so, as deemed by Main Roads. This scope must have a greater range of rules than currently exists. This should include where drivers do not have sufficient vision to make judgements (12 secs) from crests and curves and merge zones. 

Another area where lane changing should not be permitted is between any lanes close to an exit point off the motorway. On a daily basis, some drivers elect to exit the motorway by crossing up to four lanes of traffic in less than 200m prior to the exit point. This has and will continue to result in traffic accidents, fatalities and initiates multiple traffic waves.

A third area where lane changing should not be permitted is between any lanes other than the lane exiting, i.e. the first 400m from traffic entering the motorway. As traffic enters the motorway, drivers in all lanes ‘shuffle’ for road position with no genuine reason to change lanes which requires a merging manoeuvre.

The current implemented TRUM for merging traffic is inappropriate, in that it is the merging give-way rule.

Vehicles entering are mandated to give way to all traffic on the M1 (A must give way to B) and thus to merge, must break this law. The appropriate TRUM marking is ‘no line marking’, which engages the rule of give way to the vehicle in front, regardless of which lane of the two merging lanes a driver is in, refer to point 6 in the solution below.

THE SOLUTION

The following solution draws on existing road infrastructure, current TRUM laws, as well as introducing new signage and a marketing strategy. A low cost solution, especially when compared with the economic impost current ineffective traffic management is having on Southeast Queensland.

1.   Place signage at 3km and 1.5 km prior to an exit, highlighting all lanes ahead will be restricted from merging/lane changing and that those drivers intending to exit need to be in the left hand lane from this point. This prepares drivers early, and at speed to merge across lanes. Merging at speed reduces the likelihood of generating a traffic wave and daily users of the road network, will learn to be in the left hand lane early.

2.   Use the TRUM of ‘solid white line’ between all lanes from a calculated point, estimated for the purpose of this proposal as 400m prior to the exit. This road marking to be continuous until an estimated distance of 400m past the merging lane termination point, ‘no merging zone’.

3.   Compliment the solid white line with affixed line divider, which facilitates emergency vehicles to still cross while being a physical barrier to normal road users.

4.   Mark both the left hand lane and the entering merging lane with painted chevrons to set a safe following distance that facilitates merging, similar to that used on the south bound lane of the Bruce Highway near the Caloundra interchange in Queensland.

5.   Introduce New Zealand’s “Merge Like a zip” signage and advertising campaign to inform road users of this initiative.

6.   Change current merging TRUM as detailed in Volume 3, Part 2: Pavement Marking, page 187 to use the TRUM and road rule of “when lines of traffic merge, you must give way to any vehicle that is ahead of you. In this example, Vehicle B (yellow) must give way to Vehicle A (white).”:

EXPECTED RESULTS & BENEFITS

1.   Significantly reduced ‘traffic waves’ which cause severe congestion in Southeast Queensland.

2.   Engineering controls making roads safer and reduce accidents caused by merging and tailgating, thereby re-shaping driver attitudes.

3.   Economic benefits for society, including improved traffic flow that will support the use of ‘toll tunnels’, removing drivers concerns of paying a toll to then park on the South East Freeway and M1.

Join me in pushing for "cost effective" improvements that manage drivers through traffic controls and driver behaviour. Building more roads is not necessarily the best answer.