Road noise comes mostly from tyres and electric cars will not fix it

This is written to be used rather than admired. Each section below is a decision about traffic noise, and each one has a default.

Rolling noise takes over quickly

At low speeds an internal combustion engine dominates the sound a vehicle makes; as speed rises, tyre and road interaction takes over. The crossover point depends on the vehicle, the tyre and the surface, and in typical cars it falls somewhere in the range of ordinary urban driving speeds. Above that point, the sound is generated by tread blocks striking the surface, air being pumped out of the tread pattern, and the surface texture itself.

This is why a queue of stationary traffic is quiet and a free-flowing dual carriageway is not.

Electrification helps where speeds are low

Removing the engine produces a clear benefit in slow, congested and stop-start conditions, which is much of a city centre. On faster roads the reduction is smaller, and heavier battery vehicles can put more load through the tyre. Regulations in several jurisdictions now require electric vehicles to emit an artificial sound at low speed for the safety of blind pedestrians, which reclaims part of the gain deliberately.

Measured properly, expecting electrification to solve arterial road noise is a misreading of where the sound comes from.

Surfacing is the biggest single lever

Low-noise surfaces use finer aggregate, negative texture or a porous void structure that absorbs sound and reduces air pumping. Measured reductions at installation can be substantial, and they decay over the life of the surface as voids clog and texture wears.

Across a network, porous surfaces need periodic cleaning to retain performance and are less durable under heavy freight loading. A noise benefit quoted at laying is not the benefit ten years later, and maintenance regimes rarely account for that.

Speed is the cheapest control

Because rolling noise rises steeply with speed, modest speed reductions produce audible reductions in level. Smooth flow matters as well: acceleration and braking cycles produce peaks that are more disturbing than a constant level of the same average. This is one of the few areas where speed management, emissions and noise all point the same direction.

It also explains why a calmed street can sound better even when traffic volumes are unchanged.

Barriers and facades treat symptoms in the right order

Noise barriers work by interrupting the line of sight between source and receiver, so their effectiveness depends on geometry and drops away at upper floors. Glazing and ventilation upgrades protect the interior of a dwelling and do nothing for the garden, balcony or street.

Across a network, treating at source is preferable in principle and slower to deliver, which is why facade treatment dominates in practice. A scheme that only offers double glazing has conceded the outdoor environment.

Night noise is the health-relevant measure

Epidemiological research has linked long-term night-time traffic noise exposure to sleep disturbance, and through that to cardiovascular outcomes. Effect sizes are debated and confounding with air pollution and deprivation is difficult to remove entirely. What is well established is that sleep is disturbed by peak events rather than by averages, so metrics based on annual mean levels understate the problem.

Freight movements and single loud vehicles at night therefore matter disproportionately to their share of traffic.

The takeaway

Listen to a passing car. Most of what you hear is the road, not the motor.

Cities are built by a thousand small permissions, not one big plan.