Related Experiment Video
Updated: Feb 5, 2026
07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
9.0K
Safety and operational impacts of setting speed limits below engineering recommendations
Vikash V Gayah1, Eric T Donnell1, Zhengyao Yu1
1Department of Civil and Environmental Engineering, The Pennsylvania State University, 231 Sackett Building, University Park, PA, 16802, United States.
Accident; Analysis and Prevention
|September 12, 2018
Summary
Setting speed limits 5 mph below recommendations improves compliance and safety on rural roads. Higher reductions showed mixed safety results, highlighting the importance of appropriate speed limit setting.
Area of Science:
- Transportation Engineering
- Traffic Safety
- Road Safety Analysis
Background:
- Posted speed limits significantly influence vehicle operating speeds and road safety.
- Discrepancies between engineering recommendations and posted speed limits can impact driver behavior and crash risk.
- Understanding these impacts is crucial for effective traffic management and safety strategies.
Purpose of the Study:
- To quantify the operational and safety effects of setting posted speed limits below engineering recommendations on rural roads.
- To analyze the relationship between speed limit differences, operating speeds, and speed limit compliance.
- To evaluate the impact of reduced speed limits on crash frequency and severity.
Main Methods:
- Field data collection of vehicle operating speeds and historical crash data from rural Montana roads.
- Statistical modeling including linear, quantile, and logistic regression to predict operating speeds and compliance.
- Empirical-Bayes before-and-after analysis to develop crash modification factors (CMFs).
- Temporal adjustments to account for changes in data collection and traffic characteristics over time.
Main Results:
- Speed limit compliance decreased as the difference between recommended and posted limits increased.
- Heavy police enforcement reduced operating speeds and improved compliance.
- A 5 mph reduction in speed limits led to a statistically significant decrease in total and fatal+injury crashes.
- A 10 mph reduction showed decreased total/PDO crashes but an increase in fatal+injury crashes.
- Larger reductions (15-25 mph) lacked statistical significance due to small sample sizes.
Conclusions:
- Setting posted speed limits 5 mph below engineering recommendations can enhance safety and improve speed limit adherence.
- The effectiveness of larger speed limit reductions is less clear and may have unintended safety consequences.
- Optimizing speed limits requires careful consideration of operational impacts, enforcement, and potential safety trade-offs.
Related Concept Videos
02:27Limiting Reactant
70.1K
The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as stoichiometric amounts. However, in reality, the reactants are not always present in the stoichiometric amounts indicated by the balanced equation.
70.1K
01:28Survey Safety
410
Surveying near highways, rough terrain, or power lines involves significant risks. Working along highways is particularly dangerous and requires the use of warning signs and flagmen. It is safest to avoid working directly on roads and use offsets whenever possible. When highway work is unavoidable, it must follow all safety guidelines. Surveyors should wear bright clothing, such as orange reflective vests, to ensure visibility to motorists, coworkers, and hunters. In construction zones, wearing...
410
01:29The Number e as a Limit
92
The number e is a fundamental constant in calculus, playing a central role in describing continuous change, particularly exponential growth. It is most naturally defined through its relationship with the natural logarithm, which is the inverse of the exponential function with base e. This relationship allows e to be characterized using basic principles of differentiation rather than as an arbitrary numerical constant.A key property of the natural logarithm function, ln x, is that its derivative...
92
01:19Impact of Groups on Groups
250
Social psychologists analyze how groups influence one another, shaping social structures and interactions through both cooperation and competition. These dynamics manifest in various ways, ranging from economic partnerships to intergroup conflicts that shape societal structures and perceptions.Cooperation and Competition in Intergroup RelationsIntergroup relationships vary across contexts, sometimes fostering cooperation and mutual benefit while at other times leading to conflict and...
250
00:49What is Genetic Engineering?
80.3K
Overview
80.3K
01:23Types of Limits I
194
Limits are a key mathematical concept for understanding how functions behave as their input approaches specific values, particularly when the function is undefined. They help reveal trends and discontinuities by examining the values a function approaches rather than its actual value.One-sided limits focus on the direction from which a value is approached. When a function behaves differently depending on whether the input approaches from the left or the right, the two one-sided limits may not...
194