Is it legal for a Town highway department to install speed bumps at a 4-way stop?

Answer: No. 

First, speed bumps are never allowed on a public highway. A speed hump or speed table may be a possibility as part of an overall traffic calming plan. There are agencies who raise an entire intersection creating a very large speed table. 

Speed humps are used to slow traffic down, they are not for stopping traffic and use at a stop sign is not what driver would expect.

Purpose of Speed Humps

• Traffic Calming: Speed humps are designed to slow down traffic in areas where excessive speed is a concern, such as residential neighborhoods, school zones, and parking lots. They encourage drivers to reduce their speed to navigate over the hump comfortably.
• Pedestrian Safety: By reducing vehicle speeds, speed humps help enhance the safety of pedestrians, especially in areas with high foot traffic.

Purpose of Stop Signs

• Traffic Control: Stop signs are used to control traffic flow at intersections. They require drivers to come to a complete stop, ensuring that vehicles from different directions can safely navigate the intersection.
• Right-of-Way Management: Stop signs help manage the right-of-way, preventing accidents and ensuring an orderly flow of traffic.

Reasons to Avoid Speed Humps at Stop Signs

• Redundancy: A stop sign already requires a complete stop. Adding a speed hump before a stop sign is redundant because the primary purpose of speed hump is to slow down and stop signs, to stop traffic.
• Driver Expectations: Drivers expect to come to a stop at a stop sign but not necessarily to encounter a speed hump. Placing a speed hump at a stop sign can be unexpected and potentially confusing, leading to abrupt or unsafe braking. A speed table as part of an overall traffic calming plan may be feasible, but should only be done as part of a plan for a large area.
• Vehicle Control: Navigating a speed hump requires drivers to slow down gradually. If a speed hump is placed too close to a stop sign, it can complicate the process of stopping smoothly and safely.
• Traffic Flow: Speed humps can disrupt the smooth flow of traffic, especially if placed inappropriately. At an intersection controlled by a stop sign, the additional slowing effect of a speed hump can lead to unnecessary congestion and delays.

Appropriate Placement of Speed Humps

• Speed humps should be strategically placed in areas where reducing speed is necessary but not at points where a complete stop is already required. Suitable locations include:
  • Long stretches of road with no stop signs or traffic lights.
  • Approaches to pedestrian crossings.
  • Areas near schools or parks.
  • Residential streets with a history of speeding issues.

More information on traffic calming can be found in the Quick Answer listed below and the NYSDOT Highway Design Manual chapter on Traffic Calming. 

https://cals.cornell.edu/nysltap-local-roads/residential-area-wants-speed-hump-or-speed-table-what-are-they

NYSDOT Highway Design Manual Chapter 25: Traffic Calming