We regularly hear from residents about the lack of synchronized lights on Mississauga streets. Signal light synchronization is more complicated than many people realize though.

Indeed, perfectly synchronized traffic lights generally not possible, especially in a built-out city like Mississauga where the road network and traffic patterns are complex and constantly shifting. Municipalities don’t “set and forget” signals—they balance competing priorities knowing that they can only optimize some movements, some of the time.

Below is how cities typically handle it, and why people’s expectations often collide with real-world constraints.

One direction—not both

On most major corridors, engineers may choose a primary direction (e.g., east–west on Burnhamthorpe or Eglinton) and coordinate the green light wave in that direction during peak periods.

Why only one? Because:

• Traffic is heavier in one direction at a time.
• Offsetting signals for one direction automatically misaligns them for the opposite direction.

• Trying to optimize both creates a compromise that satisfies neither.

Residents often assume synchronization means “greens both ways.” Technically impossible without turning every intersection into a four-way free-flow—which cannot coexist with cross-traffic, pedestrians, or transit priority.

Even if you perfectly align every light on a long corridor, cross streets ruin the perfection instantly:

• Cross streets have their own traffic demands.
• Peak hour patterns are different on perpendicular routes.
• Cities must maintain minimum green times for safety and capacity.

Every time a cross street gets its green, the coordinated band on the main street narrows or collapses.

To compensate, municipalities often:

• Use longer cycle lengths on major roads so there’s more “room” to keep progression.
• Allow small offsets between intersections so minor disruptions don’t propagate.

It’s a constant balancing act.

Small side streets and mid-block crosswalks usually run actuated phases—they only turn red on the main road when a vehicle or pedestrian calls for service.

This is where residents perceive “the lights aren’t synchronized,” but the signal is actually doing exactly what the city wants:

• Prioritizing through-traffic until a local resident needs to cross.
• Preventing long waits for people on low-volume streets.
• Maintaining accessibility and walkability.

If the City disabled these actuated phases, you’d get steady green waves—but only by forcing pedestrians to wait excessively and overly delaying side streets. That’s socially unacceptable.

Increasingly, major corridors include:

• Emergency vehicle preemption for fire and ambulance
• Protected left-turn phases for safety upgrades
• Red-light camera timing constraints

Every one of these systems modifies the signal cycle, sometimes early-cutting or extending greens by several seconds. That unpredictability is intentional—to keep transit reliable, respond to emergencies, or prevent collisions.

Municipalities regularly retime signals—but traffic volumes today don’t match the volumes from:

• Pre-COVID patterns
• Holidays
• Back-to-school cycles
• Storm days
• New developments opening

A corridor that flows perfectly in April might be dysfunctional in November. Retiming every few months is expensive and labour-intensive, so cities typically do:

• Network-wide retimings every 2–4 years
• Spot fixes when conditions drastically change
• Real-time adaptive systems (where budgets allow)

The most advanced cities deploy systems like SCOOT, SCATS, or InSync. These:

• Continuously measure real-time traffic volumes
• Adjust cycle lengths and offsets every few minutes
• Respond dynamically to congestion, incidents, or surges

Mississauga already uses elements of adaptive control on several corridors. But even adaptive systems cannot create a perfect green wave. They simply optimize the network more intelligently and react faster when it breaks down. Furthermore, given the cost of these systems, many intersections still operate with older technologies.

Two trends are making coordination harder nationwide:

1. Safety-first design
   More protected left turns, longer pedestrian crossing times, accessible signal requirements, leading to longer cycle lengths and less flexibility.
2. Diverse travel patterns
   More short trips, more deliveries, more turning movements—less predictable volumes.

Cities are trying to maintain movement and improve safety. That conflict alone makes perfect synchronization mathematically impossible.

Many residents have experienced “perfect” green waves in other cities—usually on long one-way streets or corridors with few intersections like in Hamilton for example. One-way streets make synchronization far easier because engineers only have to coordinate traffic in a single direction, without worrying about opposing flows, turning movements, or major cross streets disrupting the pattern. With fewer variables to manage, signals can be timed so that a steady pace almost guarantees a string of green lights. In contrast, two-way arterials in suburban cities like Mississauga have to balance opposing traffic, side-street demand, pedestrian crossings, and turning movements, making that same level of synchronization essentially impossible.

Municipalities use a mix of coordinated timing, actuated signals, peak-direction prioritization, and increasingly adaptive tech. Residents perceive signals as “broken,” but in reality the network is doing exactly what it’s designed to do: balance mobility, safety, pedestrian access, transit needs, and cross-street demand.