Convert traffic congestion on arterial streets to free flow using existing infrastructure, and get fast trips and low emissions

Submitted by john on Sun, 17/06/2018 - 19:08
effect of metering

Proper operation of arterial streets will produce a green wave, where a platoon of traffic flows through sequential sets of traffic signals at the speed limit with the minimum of wasted time, braking, acceleration, and emissions. The following steps are employed as necessary:

1. Meter traffic

To prevent congestion and get a green wave, traffic must be gated or metered. Congestion wastes time, prevents signal linking, delays buses and is more costly than the alternative of restricting flow.

2. Smooth traffic flow

To cut stops in the counter-peak direction, traffic from minor streets and pedestrians must be staged across arterial traffic.

3. Increase intersection capacity

For major capacity, delay and safety benefits, right turn conflicts must be resolved on the approaches to intersections.

4. Reduce trip time and emissions

To avoid wasting time and creating emissions, the majority of drivers must jump the queues at constrictions, but for a small toll. A few drivers must queue, retaining free entry, as a low priority buffer, to avoid wasted capacity, yet constrain demand.

The impact of these steps is quantified next for an example route.

Using Hoddle St, the most congested arterial road in Melbourne, as an example, this southbound AM peak hour chart shows the variation in trip time and emissions for the steps: (a) metering; (b) increasing capacity; and (c) queue jumping. These outcomes can be translated to any other problem route such as the Alexandra Pde - Elliott Ave route.

The trip time progressively reduces from 40 minutes to 25, 16, and then a weighted average of queued time and express time of 9 minutes, causing and despite, a major increase in demand. Emissions reduce with trip time and increase with demand.

Capacity increases as a result of (a) metering and removal of bus lanes, and of (b) conversion of major intersections to 2-phase, causing a reduction of trip time, and a reduction of total queue length.

90% queue jumping cuts trip time to a minimum, when queues at the entry to the metered length are bypassed. All trips can then form part of a green wave of traffic that has a minimum of braking, acceleration, emissions and wasted time within the metered length. Time wasted in any queue also increases CO2 and particulates.

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