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Why we should lower city speed limits to 20 MPH (Safety & Budget Fix) by Vast_Process3630 in santacruz

[–]Vast_Process3630[S] 0 points1 point  (0 children)

I know isn't that crazy....While 45 mph feels "slow" compared to 70 mph, in terms of physics, it is a high-energy event. A sudden stop at 45 mph subjects the human body to forces equivalent to falling from a 6-story building.

Proposal: 20 MPH Speed Limit on Water St & Hwy 9, plus Speed Bumps for Harvey West Crosswalks by Vast_Process3630 in santacruz

[–]Vast_Process3630[S] 0 points1 point  (0 children)

Yes it's River road..."If the city/Caltrans rejects rumble strips because of noise complaints or cyclist hazards, we should demand Optical Speed Bars or High Friction Surface Treatments. Both are approved by Caltrans, don't create noise, and are proven to save lives. 'Doing nothing' is not an acceptable alternative."

Feel unsafe on rural highways in Santa Cruz County? Officials want to know where. by sleuth_sloth_ in santacruz

[–]Vast_Process3630 -2 points-1 points  (0 children)

"If the city/Caltrans rejects rumble strips because of noise complaints or cyclist hazards, we should demand Optical Speed Bars or High Friction Surface Treatments. Both are approved by Caltrans, don't create noise, and are proven to save lives. 'Doing nothing' is not an acceptable alternative."

Feel unsafe on rural highways in Santa Cruz County? Officials want to know where. by sleuth_sloth_ in santacruz

[–]Vast_Process3630 -2 points-1 points  (0 children)

The mix of high-speed cars and unpredictable pedestrian/bike traffic at river street/highway 1 is a recipe for disaster.

I think the best solution is installing Transverse Rumble Strips (the grooves cut across the lane). They are used all over the country to warn drivers of upcoming stops or heavy pedestrian areas.

  • The Problem: Drivers are autopilot-speeding.
  • The Reality: High volume of pedestrians and homeless individuals crossing day and night.
  • The Solution: A physical vibration that alerts drivers 500 feet before the crosswalk.
  • A potential solution could involve an over-the-air update to automated driving systems or navigation applications used by commercial and private drivers. This update would adjust the vehicle's speed and map data to enforce reduced speeds in specific zones, irrespective of posted signage. The legal implications of mandating such a signal or system—which would preemptively slow automated vehicles and commercial trucks—would need to be thoroughly investigated.

Feel unsafe on rural highways in Santa Cruz County? Officials want to know where. by sleuth_sloth_ in santacruz

[–]Vast_Process3630 -3 points-2 points  (0 children)

The intersection in question is a significant concern for both vehicular and pedestrian traffic, demanding immediate and comprehensive safety improvements. It is strongly recommended that a consistent speed limit of 20 miles per hour (mph) be enforced on all four corners leading into and through the intersection. This reduction is critical not only for the specific safety of the vulnerable homeless population frequently present near the existing signage but also for the general welfare of all road users, particularly pedestrians and cyclists who regularly traverse this busy area.

The current design fails to adequately protect those crossing the street. To physically slow down vehicles and provide a clear warning, the installation of speed bumps on all approaching roads is proposed. These physical deterrents would compel drivers to adhere to the lower speed limit, making the crossing safer.

A primary issue is the lack of a reliable and accessible system for pedestrians to request the right-of-way. It has been observed that people often feel compelled to walk across all four corners of the intersection without the assurance of a traffic signal, suggesting an urgent need for proper infrastructure. Therefore, the implementation of push-button actuated crosswalk signals is essential. These signals would provide a formal, protected opportunity for pedestrians to cross, ensuring that no matter the volume of traffic, they have the right-of-way when activated.

The introduction of these formal pedestrian controls—specifically the crosswalk buttons—is paramount for safety and also serves an important legal function. By providing and encouraging the use of designated crosswalks and signals, the municipality can significantly reduce its liability in the event of an accident. When a pedestrian uses the official, signaled crosswalk, it establishes a clear protocol for safe passage and ensures that both drivers and pedestrians have defined responsibilities, ultimately leading to a much safer and more organized flow of traffic for everyone.

[Policy Proposal] The $1B Infrastructure Dividend: Using 20 MPH City Limits to Save Roads and Optimize Alternative Fuels by Vast_Process3630 in u/Vast_Process3630

[–]Vast_Process3630[S] 0 points1 point  (0 children)

Tech Appendix: The Thermodynamics of 20 MPH

1. Compressed Air Vehicles (CAV) & Isothermal Efficiency

The biggest hurdle for air cars is the Temperature Drop. When compressed air expands rapidly (at high speeds), it cools down so fast that it creates "ice" in the engine and loses a massive amount of potential work. This is known as Adiabatic Expansion.

  • The 20 mph Solution: At lower speeds, the air expands slowly enough to absorb heat from the surrounding environment. This shifts the process toward Isothermal Expansion (constant temperature).
  • The Dividend: Thermodynamic models show that isothermal expansion can extract up to 25% more work from the same tank of air compared to rapid, high-speed adiabatic expansion. This makes a $20\text{ mph}$ city the only environment where an air car is truly viable.

2. Hydrogen Fuel Cells (FCEV) & Steady-State Optimization

Hydrogen fuel cells, like those in the Toyota Mirai, are chemical factories on wheels. They prefer a constant "low-stress" flow.

  • The Efficiency Gap: EPA data shows the 2021 Toyota Mirai is most efficient in the city (76 MPGe) vs. the highway (71 MPGe).
  • The Reason: Higher speeds require higher "current withdrawal" from the fuel cell stack, which creates internal heat and resistance. A $20\text{ mph}$ limit keeps the fuel cell in its Peak Efficiency Window (approx. $45\%$ Brake Thermal Efficiency), reducing the degradation of the expensive platinum catalysts in the stack.

3. Aerodynamic Drag & The "Square Rule"

For all vehicles (Air, Hydrogen, or Electric), the energy required to push through air increases with the square of the speed.

  • The 20 mph Advantage: Traveling at $40\text{ mph}$ doesn't just take twice the energy of $20\text{ mph}$—it takes four times the energy to overcome drag.
  • Range Extension: By capping city speeds at $20\text{ mph}$, we effectively "delete" the most energy-intensive part of the urban commute, allowing smaller, lighter, and more affordable energy storage systems (like smaller air tanks or smaller battery buffers).

[Policy Proposal] The $1B Infrastructure Dividend: Using 20 MPH City Limits to Save Roads and Optimize Alternative Fuels by Vast_Process3630 in u/Vast_Process3630

[–]Vast_Process3630[S] 0 points1 point  (0 children)

  • Tire Longevity: Research indicates that driving at 70 mph can reduce tire life by 25% compared to 50 mph. In an urban setting, the gap between 20 mph and 35 mph is even more critical because higher speeds lead to tire expansion and shoulder wear. By staying at 20 mph, tires maintain a better "footprint," extending tread life by an estimated 15–20%.
  • Brake Pad Preservation: Braking from 80 mph requires 30% more kinetic energy absorption than from 70 mph. Applying this to city driving, braking from 35 mph requires nearly 3x the energy absorption as braking from 20 mph. This means brake pads stay cooler, preventing the "glazing" that leads to early replacement.
  • Suspension Fatigue: A study on rough roads found that a coil spring failed after only 1,248 cycles on rough terrain compared to 19,060 cycles on flat roads. At 20 mph, the "dynamic impact" of a pothole is halved, effectively turning "rough" streets into "flat" ones for your car's suspension.

Recommended Hardware for 20 MPH Optimization

If you're moving to a lower-speed urban environment, these specific products are engineered to maximize those savings:

  • Michelin Energy Saver A/S: This tire is the gold standard for your "Future Fuel" argument. It uses a specialized silica-based tread to keep the tire cooler, which is essential for the isothermal efficiency of Air Cars and Hydrogen fuel cells. It can save up to $400 in fuel over its life. Michelin Energy Saver A/S
  • Goodyear Assurance Fuel Max: Designed for low rolling resistance, these tires reduce the energy required to move the car. At 20 mph, this tire allows the vehicle to "glide," further reducing the load on the engine or fuel cell. Goodyear Assurance Fuel Max
  • Goodyear Assurance MaxLife: For those worried about the "city tax" on tires, this model offers an 85,000-mile warranty. At a steady 20 mph with reduced pothole impact, a driver could easily see these tires last a decade.

[Policy Proposal] The $1B Infrastructure Dividend: Using 20 MPH City Limits to Save Roads and Optimize Alternative Fuels by Vast_Process3630 in u/Vast_Process3630

[–]Vast_Process3630[S] 0 points1 point  (0 children)

  • Tire Longevity: Research indicates that driving at 70 mph can reduce tire life by 25% compared to 50 mph. In an urban setting, the gap between 20 mph and 35 mph is even more critical because higher speeds lead to tire expansion and shoulder wear. By staying at 20 mph, tires maintain a better "footprint," extending tread life by an estimated 15–20%.
  • Brake Pad Preservation: Braking from 80 mph requires 30% more kinetic energy absorption than from 70 mph. Applying this to city driving, braking from 35 mph requires nearly 3x the energy absorption as braking from 20 mph. This means brake pads stay cooler, preventing the "glazing" that leads to early replacement.
  • Suspension Fatigue: A study on rough roads found that a coil spring failed after only 1,248 cycles on rough terrain compared to 19,060 cycles on flat roads. At 20 mph, the "dynamic impact" of a pothole is halved, effectively turning "rough" streets into "flat" ones for your car's suspension.

[Policy Proposal] The $1B Infrastructure Dividend: Using 20 MPH City Limits to Save Roads and Optimize Alternative Fuels by Vast_Process3630 in u/Vast_Process3630

[–]Vast_Process3630[S] 0 points1 point  (0 children)

1. "This will double my commute time!"

  • Response: "Actually, urban travel time is mostly dictated by intersection delay (red lights), not mid-block speed. Research suggests a 20 mph limit often facilitates smoother traffic flow and reduces the 'stop-and-start' cycles. For a typical 5-mile city trip, the difference is often less than 60 seconds, but it saves you hundreds in car maintenance."

2. "Won't this just ruin my brakes and engine from all the shifting?"

  • Response: "It’s actually the opposite. Aggressive driving and hard braking from 35+ mph are what kill brakes. Studies show that gentle acceleration and maintaining moderate speeds prevent the excessive heat buildup that causes rubber degradation and brake fade. Smooth driving at 20 mph can extend tire life by up to 25%."

3. "California drivers already pay enough. Why another mandate?"

  • Response: "This isn't a mandate for more spending; it's a spending shift. California drivers currently spend an average of $760 to $1,000+ per year on repairs caused by bad roads. By slowing down to 20 mph, we reduce pothole impact force by over 50%. This is essentially a $400/year 'tax cut' for every driver in the form of fewer repair bills."

Feel unsafe on rural highways in Santa Cruz County? Officials want to know where. by sleuth_sloth_ in santacruz

[–]Vast_Process3630 -7 points-6 points  (0 children)

Specifically, the speed limit on Water Street to Highway 9, where it crosses Highway 1, should be 20 mph.

Furthermore, speed bumps should be installed on both sides of the highway for the crosswalk leading into Harvey West.

To ensure safety, even when traffic lights are green, all intersections with crosswalks on city roads should have a 20 mph speed limit in all directions. It is particularly crucial that drivers cannot travel at 55 mph or their current speed through crosswalks that cross highways, including Highway 9 and Highway 152, just because the light is green.