Advocacy: Why We Do What We Do
Mike Watson | Advocate Coordinator , Pedal Power ACT
Chapter Five: Speed and Its Implications
Speed plays a huge role in how we design and use transport networks. This story isn’t about speed limits or road rules; it’s about how you, as a sentient human, assess and manage the risks of moving quickly. From a human factors perspective, we’ll explore how you perceive hazards, how you react to them, and why your brain sometimes struggles to keep up at higher speeds. Future chapters will connect these instincts to infrastructure design and the rules of the road (and off-road routes).
Speed Changes Everything
It gets you to your destination faster.
It can make travel more exciting, but also more dangerous. · It forces you to shift your ‘focus of attention’ ahead to stay safe and react in time.
When you’re no longer confident in your ability to stay safe, the consequences of mistakes escalate, and they escalate fast.
Here’s the science in simple terms:
Double your speed and you’ll get there in half the time (linear).
But it takes four times the energy to accelerate to that speed from a stop (speed squared).
And the stopping distance also increases by about four times, because tyre grip changes with speed.
So, as you go faster, your attention needs to move further ahead to spot and plan for hazards. If you’re confident, you can avoid them, great. If not, fear kicks in, and you may instinctively choose to reduce speed and minimise the impact of any potential collision.
Instinctive Collision Avoidance
How do we naturally avoid crashing into others? Sometimes we rely on road rules: in Australia, we pass on the left; in Algeria, on the right. But what about when there are no rules, like in the open Sahara Desert where you can pass kilometres apart?
Your brain doesn’t visually focus only on the oncoming vehicle. Instead, it tracks how that vehicle moves relative to the background. If the vehicle appears to move sideways against the stationary backdrop, and both vehicles hold course and speed, you’re safe. But does it stay fixed relative to the background in your field of vision? Danger. That’s your cue to adjust your speed or direction.
This “see and avoid” instinct starts young. You unconsciously use it every day: weaving through a crowd, dodging players on a sports field, sailing on a lake, or approaching a
cyclist on a shared path. It works as long as at least one person in the “conflict pair” sees the other and reacts.
When “See and Avoid” Fails
Sometimes collisions happen because:
Neither person notices the potential conflict until the last moment.
One person who isn’t aware of the conflict makes a sudden, unpredictable move without realising someone else is nearby.
In these situations, the aware traveller often raises an aural alarm, shouting, yelling, or ringing a bell if they’re on a bike. This snaps the other person’s attention to the conflict. Once both parties are aware, their instincts kick in, and they should instinctively cooperate to avoid a crash. We call this “alerted see and avoid.”
The risk of a collision drops dramatically when:
Both people are aware of each other early.
There’s enough space for one person to give way, even if the other isn’t paying attention.
If you’re unsure whether someone has seen you, slow down or make a sound to alert them. On a bike, a bell is highly effective; most people immediately associate it with an approaching cyclist and look up (though some may be distracted by headphones or their phones).
The Takeaway
Understanding how speed shapes our attention, reactions, and instinctive behaviours is helpful for staying safe on two wheels. The faster we go, the less time we have to see, plan, and avoid hazards, but with awareness and small adjustments, we can reduce risk. Whether it’s shifting your focus further ahead, slowing down in good time when unsure, or using your bell to alert others, these simple habits keep everyone safer.
This chapter unpacked the theory of how not to collide – anywhere - even on a bike. Understanding these instinctive human behaviours can make your travels smoother and safer. In the next chapter, we’ll explore how these instincts play out in practice across different riding environments.
If you’re curious about how these challenges apply in other fields, there’s a fascinating paper that dives into similar dynamics in completely different settings, which you can read here.
