Posts Tagged ‘signal’

green light, go light

Wednesday, August 17th, 2016

green light, go light

When it comes to traffic lights, there is a clear favourite: no one likes red, but everyone loves green. And those advanced green arrows are great, except that they never seem to last long enough. Seriously, traffic signals are one of those aspects of commuting that we all have strong feelings about. But what determines when a light changes from red to green, and how long that advanced green should last? Let’s try to shed some light on that…

There’s nothing random about the timing of traffic signal phases, and their design has only one goal: to move traffic and pedestrians as freely and safely as possible along our roadways. As with all aspects of civil and urban design, things are more complicated than they might seem, requiring clear priorities and tradeoffs to balance out everyone’s needs. Here are the basics.

In traffic engineering-speak, a signal phase refers to the operation for all approaches to an intersection [e.g., a red light will show for a side street at the same time as the main road has a green light]. A cycle is the entire combination of phases for an intersection [red, green, amber, advanced green etc.]. A cycle can range from 90 to 160 seconds [meaning if you miss a green light, that’s how long you could wait until the next one], although the timing depends on the intersection and the time of day.

Determining what phases are needed for the cycle, and how long each phase will last, reflects the needs of all users – including transit, pedestrians, cyclists and drivers. Some phases in the cycle length ensure that road users are not in conflict with one another [for example, drivers can’t exit a side street at the same time as drivers are going straight through on the main road]. Also, some users’ needs will be parallel within a phase – e.g., pedestrians, transit and drivers all travelling in the same direction.

Decisions about phases, and how long they last, take into account actual traffic volumes and how traffic patterns change throughout the day. Timing is designed to make the intersection work as efficiently as possible [meaning moving through the largest numbers of users], and minimize delays for all road users [although with many roads at or over capacity during rush hour, signal timing alone can’t solve congestion]. Signal priority is also provided to fire, ambulance and transit, where the signals change to provide priority right-of-way to emergency vehicles and some transit vehicles, without violating the pedestrian timings.

Timing for each phase is based on the minimum timings required by provincial standards. These include minimum timings for pedestrians, motorist and vehicle clearance [amber and red timings] based on several factors, including the width of the intersection, and traffic speed [posted and operating].

Proximity to other infrastructure also has an impact on priorities and the timing of phases. For example, the Ontario Ministry of Transportation may have jurisdictional control over the timing of lights at some intersections, depending on how close the intersection is to a provincial highway off-ramp or railway crossing.

Ultimately, any one cycle has only so many seconds, and no one wants to wait longer than they have to. So the design of traffic signals needs to balance everyone’s needs, while working out the best way to move traffic through an intersection and along a thoroughfare, and minimizing delay for all road users. York Region’s Traffic Signal Operations department continually reviews and assesses the performance of the region’s 848 signalized intersections, and adjusts signal timing to get people moving as freely as possible. Please contact traffic@york.ca if you have any traffic signal concerns.

Whether you’re crossing intersections on foot, bus, bike or car, traffic signals are there to move everyone along safely.

 

engineering for better traffic operations

Thursday, January 22nd, 2015

engineering for better traffic operations

You may not know this, but the vivaNext segments already open or under construction involve much more than building a cutting-edge Bus Rapid transit [BRT] system. One of the goals is to support the improvement of York Region’s transportation network, so that it works better for all travellers whether they’re going by transit, foot, bike or car. But before improvements can be made, a lot of work needs to be done to identify the constraints and how they can be fixed. This is where the complex specialty known as “traffic engineering” comes in.

You might think all traffic problems stem from too many vehicles using not enough road space. In fact, it’s much more complicated than that. Effective transportation systems [including roads] have a direct impact on our quality of life and depend on a wide range of components to work well together so that people and goods can get around. Traffic can get bogged down when key pieces are outdated or poorly designed, whether they’re related to road layout, placement of intersections, speed, traffic signal timing, turning lanes or many other components.

Traffic engineering involves the analysis, design and planning of many of those technical components. As a discipline, it studies how traffic operates and flows, how roadways are designed and controlled, and how best to plan for future roadway networks and transportation systems to support future land use. This includes coordination of the many traffic lights and the length of time of each light.

The scope of components our vivaNext traffic engineers have analyzed, modelled and designed is very broad, and takes into account York Region’s future growth over the next many years. Well beyond the design of the rapidway, we’ve looked at many issues including the site, and users, of future developments; traffic speed and flow; parking; cycling facilities; impacts from the rapidway on right- and left-turning traffic; impacts on side-streets and neighbourhoods; safety for pedestrians and cyclists; traffic signs; signalized intersection design and equipment – to name a few. And all this analysis and modelling is done in conjunction with other work focused on transit priority measures and intelligent transportation systems.

There is a huge body of science behind the specialized discipline of traffic engineering which enables us to accurately model future impacts of design alternatives, allowing us to determine which approach will help traffic move best. With new technology, traffic controllers at York Region monitor major roads on an on-going basis using traffic cameras. And from time to time, they also go back to data collected from that very low-tech approach, of simply counting cars in order to keep everyone moving along smoothly!

At the end of the day, traffic engineers are key players in developing strategies that will improve the overall transportation network, and ensure that an ever-increasing number of users on foot, on a bus, riding a bike or driving a car – are able to get around as quickly and smoothly as possible.