Commentary: Why clearways are no silver bullet

Posted: September 25, 2014 in Transport
Tags: ,

Finance reporter Alan Kohler wrote yesterday about how he believes clearways, the removal of on-street parking from major roads to improve traffic flow, are needed outside of peak hour as congestion problems now last well outside of peak hour; particularly so on weekends. In many cases a 4 lane road dedicates 2 lanes to parking, which restricts the maximum capacity by 50%. Rather than building expensive new roads, Mr Kohler opines that a better option would be to unlock this existing capacity.

Mr Kohler is right about one thing, this is definitely a much cheaper way of improving road capacity than building new roads. Sydney’s WestConnex and Melbourne’s East-West Link alone are reported to cost $11.5bn and $18bn each, with State and Commonwealth Governments contributing a combined $9.3bn to the road projects so far. But removing on-street parking will only dramatically improve traffic flows if parking is the major bottleneck. In many cases, removing on-street parking can just see it replaced by intersections and bus stops as the bottleneck.

Removing on-street parking removes one bottleneck, but often only sees it replaced with other bottlenecks. Bondi Road, nominated as a possible all day clearway by the NSW Government, shows how bus stops without bus bays and intersections without turning lanes can cause through traffic to get stuck behind buses and other cars when clearways are introduced. Click to enlarge. (Source: Google Maps, modified by author.)

Removing on-street parking removes one bottleneck, but often only sees it replaced with other bottlenecks. Bondi Road, nominated as a possible all day clearway by the NSW Government, shows how bus stops without bus bays and intersections without turning lanes can cause through traffic to get stuck behind buses and other cars when clearways are introduced. Click to enlarge. (Source: Google Maps, modified by author.)

A major road without additional turning lanes at intersections can see delays as through traffic is delayed by cars waiting to turn. However, because parking is not allowed near intersections, this effectively creates turning lanes. Thus, through traffic does not get stuck behind cars waiting to turn. This isn’t particularly problematic during peak hour as most traffic is through traffic headed towards a few major centres . However, outside of peak hour and on weekends in particular trips tend to be dispersed and this encourages more turning movements rather than through traffic. The effect of this is to enhance the benefit of clearways during peak hour but diminish it outside of it.

The absence of bus bays can also cause through traffic to get stuck behind buses picking up or dropping off passengers at bus stops. With on-street parking, bus zones act as de facto bus bays, allowing buses to pull in and allow through traffic to continue undisrupted. However, unlike turning lanes, this is a bigger problem during peak hour when buses are more frequent.

(There are alternatives to improving traffic flows. Putting aside additional investments in public transport to encourage car users out of their cars and into public transport or even considering bus lanes rather than clearways, the best way to allocate scarce resources is to put a price on it – in this case by pricing both driving and parking. Alan Davies has written on road pricing here and here, while Paul Barter explains how better pricing of parking can cut congestion.)

Extending clearways by removing on-street parking can improve traffic flows, but not all of the time. Care needs to be taken to ensure that doing so will actually improve traffic flows and not just replace one bottleneck with another. The best possible outcome is that these are considered on a case by case basis to improve traffic flows where it is possible rather than where it is not. The worst possible outcome would be that this does little to improve actual traffic flows but instead gives the impression that it will, encouraging extra road users into their cars and thus worsening traffic congestion.

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Comments
  1. JC says:

    Clearways also have an effect oin traffic generation. Like new roads, they increase capacity an speed in the short term and therefore induce people into thier cars away from PT and local trips. The effect in quality of life is also important. King St Newtwon is a pleasant destination for casual shopping, interaction etc on weekends – but a nightmare during the week because of the noise, smell and threat of injury posed by fast (and heavy truck) traffic. Perhaps if Parramatta Road was not so unpleasant we wouldn’t have to drive on it to get to nicer places to shop.

    But to hark back to the basic premise of motorways on the main dense core of Sydney. The traffic is point to point and local – it is not mythical through traffic with no origin or destination. It won’t go away no matter how much capacity you build – PT and shorter local pedestrian trips are the only way.

  2. Dylan Nicholson says:

    But clearways mean less parking, and reducing parking availability (especially free parking availability) is surely one of the best ways to encourage people not to rely on cars for trips where alternatives are available. FWIW, as a cyclist, on-street parking is generally a serious problem because of the risk of dooring, but on the other hand, many roads with 2 lanes leave little if any room for cyclists when clearways are in effect.
    The other issue with on-street parallel parking is the risk and time involved of having drivers get in and out of car-parks. We’ve all seen people hold up traffic as they need 4 or 5 attempts to squeeze into a spot that’s probably too small, and again, primarily as a cyclist, the danger of cars moving both in and out of parking spots is a constant one on many busy streets.
    On balance, I’d rather see on-street parallel parking phased out, provided that space is made available for bicycle lanes.

  3. Simon says:

    Turning lanes and bus stops only hold up traffic when vehicles are turning and buses are stopping respectively, whereas a parked car holds up traffic for 60 minutes of the hour.

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