20mph Speed Limits – A Bumpy Road for Your Car’s Health
The Mechanical and Practical Drawbacks of 20mph Speed Limits
The implementation of 20mph speed limits on many roads in Wales aims to improve safety, but this lower speed restriction results in some mechanical and practical drawbacks for vehicles.
Increased Mechanical Wear and Strain
The frequent speeding up and slowing down in stop-and-go traffic caused by 20mph limits leads to greater mechanical wear on cars compared to smoother higher-speed driving. According to an AA study, driving at 20mph increases brake usage by over 60% compared to 30mph. The increased acceleration from more stops also strains engine components.
This heightened brake usage at lower speeds can shorten the lifespan of brakes considerably. With the average brake pad replacement costing over £100, more frequent changes will raise maintenance costs. The braking system is just one component affected.
Transmissions also suffer greater wear from the constant gear changes in stop-and-go conditions. Clutches endure higher friction requirements to get moving from a standstill in a higher gear. And more rotation of the tyres over the pavement at slow speeds can accelerate tread deterioration.
According to the Government’s Emissions Analytics, tyre wear increases by up to 25% when driving at 20mph instead of 30mph. All of these mechanical factors combine to take a toll on cars and mean higher garage bills for owners.
Increased Emissions & Lower Fuel Economy
Beyond increased mechanical wear, there are other drawbacks to 20mph limits. The continuous acceleration and braking required in congested, low speed motoring burns through fuel less efficiently than smooth higher speed cruising does.
Experts point out that modern car engines are designed for optimal fuel efficiency between 30-50mph. At slower speeds, the engine operates less efficiently, burning around 20% more fuel according to emissions analytics firm Emissions Analytics.
This fuel consumption can be exacerbated by older vehicles that lack sophisticated engine management systems to optimize lower speed operation. In urban areas, the increased stop-start driving pattern further reduces miles per gallon, as acceleration requires significant fuel compared to steady speed cruising.
The environmental impact of increased emissions may seem minor on an individual car basis. But multiplied across all vehicles on the road, the collective impact in emissions from reduced fuel economy can be significant.
Some analysts argue that rather than improving air quality, lower speed limits may inadvertently increase localized pollution from concentration of vehicle exhaust during congested urban motoring. More idling and stop-start driving counterintuitively contributes to emissions issues.
Greater Journey Times & Driver Frustration
By limiting speeds to 20mph, total journey times are extended. This means time spent traveling or commuting in the car rises. For example, a 5-mile trip at 30mph takes 10 minutes, while at 20mph it requires 15 minutes – a 50% increase.
Moreover, because traffic flow is hindered, trips may take disproportionally longer in congested urban areas. Having to constantly accelerate and brake from stops increases trip duration and aggravates drivers. The dense traffic and inability to reach faster cruising speeds can leave drivers frustrated.
Increased urban congestion also takes a toll on suspension components from endless speed bumps installed to enforce the lower limits. And the combination of longer trip times in bumper-to-bumper traffic ups the risk of minor fender benders, creating additional repair costs.
Between longer journeys, reduced fuel economy, and greater wear and tear, the costs of owning and operating a car rise substantially with 20mph limits. For urban dwellers relying on their vehicle for commuting and errands, these negative impacts can become burdensome.
Potential Safety & Environmental Trade-Offs
Advocates argue that despite drawbacks, lower speed limits improve pedestrian, cyclist and driver safety. Slower vehicle speeds allow more response time and reduce accident severity.
However, some studies suggest the safety benefits are lower than anticipated. For example, Edinburgh Napier University found no significant difference in accidents between 20mph and 30mph zones. And casualty reduction has been less than predicted.
There are also concerns that focusing solely on speed limits ignores other critical road safety factors:
- Driver awareness and behaviour
- Education of cyclists and pedestrians
- Law enforcement on dangerous driving
- Street infrastructure improvements
Without accompanying public awareness campaigns and stricter enforcement, safety gains may be limited. And the costs to vehicles could simply rise without commensurate societal benefits.
Some opponents contend lower urban speed limits are an indirect attempt by officials to discourage personal vehicle use in cities for environmental reasons. But compelling people out of cars may have unintended consequences:
- Public transport may lack capacity to absorb commuters diverted from cars
- Congestion taxes and urban tolls would more directly impact driving behaviours
- People may continue using vehicles despite costs and frustrations
- Lower income individuals rely more heavily on personal vehicles
Rather than a blanket 20mph limit, a more nuanced approach could involve:
- Safety-based assessment of roads to determine appropriate speeds
- Special lower limits in high pedestrian areas like city centres
- Part-time 20mph speeds in school zones
- More flexibility for main arteries and non-residential areas
- Alternatives like congestion charges or parking fees
In summary, 20mph speed limits aim to improve safety but also create significant drawbacks to vehicle owners through increased costs and frustrations that must be weighed. A balanced approach considering all perspectives may yield better outcomes.