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Nurturing Safer Streets: A Comprehensive Guide to Speed Limits

Speed limits generally align to the nearest 10 mph increment of the adjusted 85th percentile speed. PHOTO: Joshua Hoehne / via Unsplash

Speed limits generally align to the nearest 10 mph increment of the adjusted 85th percentile speed. PHOTO: Joshua Hoehne / via Unsplash

Speeding motorists pose grave risks to pedestrian safety, especially in residential areas and around schools. Excessive vehicle speeds give vulnerable road users little chance to avoid collisions. For communities aiming to calm traffic and cultivate safer streets, implementing thoughtful speed limits is a critical first step.

How Speed Limits Are Determined

Speed limits originate from traffic engineers conducting detailed speed surveys on individual road segments. Using radar, they measure the speeds of free-flowing traffic when unaffected by signals or congestion.

The 85th percentile speed – the speed not exceeded by 85% of observed vehicles – provides the baseline for determining the speed limit. Engineers adjust this number based on contextual factors like crash data, road design, pavements, schools, and housing density.

Speed limits generally align to the nearest 10 mph increment of the adjusted 85th percentile speed. Limits are not set arbitrarily low for revenue from tickets or artificially high to enable speeding. Data-driven assessments aim to determine the safest maximum speed based on roadway conditions.

Factors Influencing Appropriate Speeds

While data guides speed limit setting, human factors also influence appropriate velocities. Driver attentiveness, experience, vision/hearing ability, and reaction times vary. Vehicle braking performance differs with tire traction, brake condition, and weight.

Environmental factors like rain, fog, and sun glare necessitate slower speeds. Roadway elements impact safe velocity too. Curves, lane width, parking, bike lanes, pedestrian crossings, and pavement volume all warrant lower speeds than straight, unobstructed roads.

With many variables at play, it is prudent to post limits below maximum safe speeds to allow margins for driver and environmental variability.

School Zones

Children have less experience judging safe crossing times. Their small size makes them harder for drivers to spot. These vulnerabilities make reduced school zone speed limits essential. Limits of 15-25 mph are typical when children are present.

Flashing beacons, playground signs, and 30mph signs cue drivers to slow down. Bright sign colors, neon flashers, and painted speed numbers on roadways all increase visibility.

Zones should extend 500-1000 feet around schools depending on configuration. Crossings, lollipop men and women and adequate parking help prevent double parking and haphazard pedestrian movements.

Vigilant enforcement of school zone limits improves compliance. Automated speed cameras provide consistent 24/7 monitoring. Engineers should assess pedestrian volume patterns to optimize school zone times and locations.

Residential Streets

Local streets with housing present special pedestrian risks, especially for children, senior citizens, and disabled residents. Limiting speeds to 20-25 mph improves safety on residential roads and marked crossings at busy junctions signal motorists to watch for pedestrians.

Speed humps spaced 300-600 feet apart physically force slower speeds between them. Carriageway width, parking, and visual clutter like low fences, trees, and signs all psychologically prompt drivers to slow by enclosing the view. Neighborhood entry treatments such as painted road sections, signs, medians, or roundabouts grab attention upon entering and condition slower driving.

Variable Speed Limits

Static speed limit signs struggle to accommodate diverse conditions across times of day. Engineers are implementing more dynamic speed limits that can adapt to evolving roadway circumstances.

School zone flashers that operate only during peak arrival/dismissal windows are one example. More advanced systems utilize digital signs with adjustable displayed speeds synced to sensors monitoring traffic, weather and even crash records in real-time.

Daily commuting “rush hour” windows might dictate lowered limits to match decreased optimal speeds from congestion during high-volume periods. Inclement weather could trigger slower limit displays. When conditions warrant increased caution, digitally alterable speed limits can flexibly reflect ideal velocities.

Methods for Improving Compliance

Well-intentioned speed limits only enhance safety if most drivers comply. Various methods aim to improve adherence to posted speed restrictions. Signs with embedded radar speed displays provide immediate feedback so motorists can judge and adjust their speed.

Traffic calming designs like squeeze lanes and speed humps physically force deceleration. Landscaping, lighting, and curb treatments create optical illusions, giving a perception of increased speed. Regular, highly visible police enforcement increases deterrence, and fines can scale with violation severity.

Speed and red-light cameras provide broad monitoring of compliance. Nevertheless, community awareness campaigns focused on safety over punishment help foster a culture of voluntary responsible driving. This nuanced “hearts and minds” approach elicits buy-in and lasting change.

Other Complementary Measures

Speed limits alone cannot guarantee pedestrian safety. They should be implemented in conjunction with other accommodations. Generous pavements with buffers give vulnerable road users ample protected space. Marked crossings, pedestrian islands, curb extensions, and lighting all enhance crossing visibility and safety. Supported left and right turn pockets prevent dangerous lane blocking.

Cycle lanes or shared lane markings reinforce separation from faster vehicles. Access management policies limit driveway cuts across pavements. Parking restrictions maintain sight lines near crossings and bus stops.

Lower speed limits coupled with pedestrian-friendly infrastructure create synergistic effects for maximizing safe mobility. Comprehensive planning is needed so speed limits do not occur in isolation.

In conclusion, appropriately set and enforced speed limits are invaluable for promoting the safety of pedestrians, cyclists, children, and residents on neighborhood streets. Nonetheless, maximum benefits require holistic planning that considers supportive physical designs, community engagement, and flexible use of technologies. Speed limits themselves should derive from data but allow for human variability.

A combination of prudent posted speed restrictions and context-specific engineering improvements can help nurture safer streets. With thoughtful implementation, speed limit policies have the potential to shift community attitudes and foster long-term culture change that genuinely revitalizes public spaces by restoring priority to vulnerable road users.

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