Smarter Buses Series – Pt 7 – Shoulder Lanes, Lane Widths and Ghost Lanes

This is part six of my series looking into how we can make big improvements to bus journeys through relatively small changes.

• In part one I looked at Khyber Pass and the need for us to be more flexible in providing better bus lanes.
• In part two I looked at how better bus priority measures can help improve the quality of our town centres.
• In part three I looked at Great South Road between Newmarket and Ellerslie
• In part four I looked at some of the changes we need to make to Link Bus services
• In part five I looked at some issues with the process for setting bus and transit lanes
• In part six I looked at improvements to dwell times and more active bus operational management

For part seven of this series, we are going to look a the importance of lane widths, how to do smarter shoulder bus lanes, and about ghost bus lanes.

Shoulder Bus Lanes

Shoulder bus lanes are basically the equivalent of kerbside lanes on a motorway and the space generally exists anyway for cars that break down. Shoulder lanes can therefore be a cheap and effective way to provide bus priority. They exist in a number of place, most infamously on the Northwestern Motorway where NZTA made the worst transport planning mistake in the past decade by building shoulder lanes rather than the much-needed busway.

For shoulder lanes to work, they need to be designed right, which means making them wide enough, taking them through or around the motorway interchanges.

Width is Key

Lanes need to be wide enough (i.e. more than 3 metres) otherwise it is too tight and you will find drivers won’t like using it. This is the big issue as the designer usually squeezes the shoulder bus lane down to provide for wider general traffic lanes.

Motorway Interchanges

Interchanges are another problem with shoulder bus lanes as they usually end at on/off ramps meaning that buses have to merge in/out of traffic or buses get stuck between queuing traffic which creates a mess for all users. The best way to deal with this problem is to skirt the shoulder bus lanes around the interchange then provide span for the lanes to go under.

This means the shoulder lanes can be continuous while general traffic and buses don’t need to merge in/out of each other. A good example of this thinking is Citybound on the Northern Motorway at Onewa interchange.

Another possible way would be better use of technology using smarter signals

1. Have ramp signals at any motorway on-ramp that conflicts with a shoulder bus lane and link them to the buses, staying red long enough to let the bus pass through without merging car;
2. Making a lane a dedicated off-ramp approach stacking lanes with the ramp signal linked to the buses, when the bus comes to merge back in the ramp signal would go red allowing the bus to do so unhindered.

So shoulder bus lanes can work well if

1. They are wide enough not just 3m;
2. Integrated well with the motorway interchanges;
3. If the route doesn’t have any motorway interchanges in between for example the SH20B future rapid transit corridor from Puhinui motorway interchange to the bridge;

The reason we need to get the design of bus lanes right is to avoid them become “ghost lanes”. Ghost lanes are where there are bus priority measures that zero sense so never get used. For example, there are kerbside bus lanes implemented on the northbound approach to Great North Road motorway interchange. Of course, this makes zero sense because buses need to use the right hand lanes to get through the motorway interchange, and the leftbound lanes are used for cars heading both east and west along the north-western motorway. Why would you want to use a bus lane for a few seconds, only to have to merge across multiple lanes against queuing on-ramp traffic as you are continuing down Great North Road not getting onto the motorway?

Let me know in the comments section what your “favourite” ghost bus lane is, and how we can fix it.

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