Residential Neighborhood Cut-Through/Intrusion Analysis for the project in City of Pasadena

Residential Neighborhood Cut-Through and Intrusion Analysis

In assessing a development project’s transportation impacts, a Residential Neighborhood Cut-Through/Intrusion Analysis is essential to determine how the project may generate unwanted vehicular cut-through traffic within nearby residential neighborhoods. The focus of this analysis is to evaluate the potential for vehicles to divert onto local residential streets, increasing traffic volumes and speeds beyond what these streets are intended to support, which can lead to detrimental impacts on the quality of life for neighborhood residents.

Residential neighborhoods are typically designed for low traffic volumes and speeds, providing safe environments for residents, especially pedestrians and cyclists, and reducing traffic-related noise and pollution. However, new development projects may lead to increased volumes and speed of through-traffic—referred to as “cut-through” or “intrusion” trips—on these local streets, thereby undermining the intended use and character of the neighborhood.

Scope of Analysis: Identifying Residential Street Segments for Evaluation

In this analysis, residential neighborhood street segments are limited to roadways classified as “Access” or “Neighborhood Connector” in the City’s Streets Plan (refer to Attachment D). These streets primarily serve residential areas, with housing along one or both sides, and are meant to function as connectors within neighborhoods rather than routes for through-traffic.

Cut-through trips are defined as vehicular trips that pass along a residential neighborhood street segment without directly accessing a destination within the area served by that roadway. These trips may be routed to or from destinations located outside of the neighborhood, or they may occur as a result of congestion on major nearby corridors, causing drivers to divert onto local streets in search of faster alternatives. However, if a project generates trips to or from locations accessible only by that specific neighborhood street, such trips do not fall under the category of “intrusion” or “cut-through” as they are not avoidable nor redirected by the existence of other, faster routes.

Conditions for Analyzing Cut-Through and Intrusion Effects

Residential neighborhood street segments must be assessed for potential cut-through or intrusion traffic impacts when:

1. The Proposed Project Requires a Local Mobility Analysis: Projects that are large enough to generate substantial traffic volumes are typically required to prepare a Local Mobility Analysis, which examines local street conditions to determine if the project will impact mobility for all users within the surrounding area.

2. Street Segment Characteristics: The street segment under study must meet the criteria for a neighborhood residential street as defined by the city’s classifications (either as an “Access” or “Neighborhood Connector” with residential uses on at least one side of the street).

In addition to the above conditions, the following criteria must be met to warrant a cut-through analysis on any given residential street segment:

• Direct Impact on Street Segment: The project is expected to add vehicular trips to a neighborhood residential street or impact its operations.

OR

• Proximity to Congested Corridors: The project is situated near intersections along a major roadway (a “City Connector”) that operates below acceptable standards (i.e., unacceptable LOS) during peak hours. If the neighborhood street segment provides a feasible, nearby alternative route that drivers may use to bypass congestion on the main corridor, it may be subject to increased cut-through trips. In these cases, DOT staff must determine the viability of the alternative route during the scoping process.

Steps for Conducting the Analysis: Data Collection and Methodology

When the above conditions indicate the need for a Residential Neighborhood Cut-Through/Intrusion Analysis, a series of steps must be undertaken to collect relevant data and apply a consistent methodology in projecting traffic impacts on residential neighborhood streets.

Step 1: Data Collection and Research

The first step involves gathering baseline data on traffic volumes and collision histories along the study segments. This data provides a benchmark against which future project-related changes can be compared, revealing the extent to which a development may increase traffic on these streets.

• Traffic Counts: Average Daily Traffic (ADT) counts should be conducted along each study segment, in line with established traffic count methodologies. This should include at least 24 hours of bi-directional traffic data to accurately reflect daily vehicle volumes and identify peak and off-peak travel patterns.

• Collision History: Analyzing the recent collision history along study segments and adjacent intersections is critical to understanding existing safety conditions. Collision data may be accessed through the Statewide Integrated Traffic Records System (SWITRS) or obtained from DOT staff. This data can help identify whether increased traffic might exacerbate any existing safety issues or necessitate additional measures.

• Field Observations: In-person observations of traffic flows are an important qualitative component of the analysis. Field observations should be conducted during both peak and off-peak hours and should document any violations of traffic restrictions, such as posted turn restrictions, signs, or diverters. Observers should also take note of any visible issues that may indicate cut-through problems, such as overflow parking, excessive traffic, or drivers disregarding neighborhood access restrictions.

Step 2: Methodology for Analysis

Using the data collected, the analysis should model both existing and future conditions to assess how traffic patterns may evolve with the project in place.

1. Future Traffic Forecasts: Forecasting future ADT volumes on residential streets involves applying an annual growth factor and incorporating the traffic generated by related or cumulative projects in the area. This provides a reasonable projection of the background traffic environment that will exist in the project’s build-out year, independent of the project itself.

2. Traffic Assignment: Project-generated traffic should then be added to the study segments, with net new traffic assigned according to the development’s projected trip generation rates and distribution patterns. In cases where intersections nearby operate below acceptable LOS standards during peak periods, an estimate should also be made of trips that may divert from congested corridors onto residential streets as a result of further delays caused by project-generated traffic.

3. Diverted Trip Estimation: This analysis considers only new cut-through trips that are likely to be diverted from major corridors specifically due to traffic conditions deteriorating as a result of project-generated traffic. Existing cut-through trips resulting from current congestion are assumed to be accounted for in the baseline ADT count data.

Step 3: Assessment Criteria for Impact

Once future ADT levels on neighborhood streets have been forecast, the analysis evaluates whether project-related increases in ADT meet or exceed specific thresholds for impact. These thresholds vary depending on the baseline ADT level of each study segment, as shown in Table 3-1 below:

If the increase in ADT on a study segment exceeds these criteria, the project is considered to have a negative effect on the residential neighborhood, potentially warranting corrective measures.

Improvement Measures: Mitigating Negative Effects

If the Residential Neighborhood Cut-Through/Intrusion Analysis reveals that a project will increase ADT on residential streets beyond acceptable levels, measures to discourage or mitigate this increase should be developed. Possible mitigation strategies, subject to DOT approval, include but are not limited to the following:

• Enhanced Average Vehicle Ridership (AVR) Targets: The project may be required to adopt a more aggressive AVR target than the city’s standard, increasing the emphasis on carpooling, public transit, and active transportation as outlined in an enhanced Transportation Demand Management (TDM) Plan in compliance with the City’s Trip Reduction Ordinance (TRO).

• Turn Restrictions and Revised Access Plans: Limiting turning movements to and from project driveways or access points can reduce cut-through traffic on neighborhood streets. Additionally, a reconfiguration of project access to minimize impacts on nearby residential segments may be considered.

• Speed Control Measures: Physical traffic calming measures, such as speed humps, may be installed along affected neighborhood streets. Such installations must comply with the city’s speed hump policy, which aims to enhance safety while maintaining access for emergency services.

• Neighborhood Gateways and Diverters: Curb extensions, diverters, and raised median gateways can help reduce cut-through traffic and reinforce the residential nature of neighborhood streets by creating a physical distinction between main and residential streets.

Selection of Appropriate Measures

The selection of specific mitigation measures should be made with consideration of the collision history, observed traffic conditions, and unique characteristics of each neighborhood street segment. These measures aim to minimize the project’s impact on residential neighborhoods, preserving their character and ensuring safe, livable environments for residents.

In summary, the Residential Neighborhood Cut-Through/Intrusion Analysis serves as a vital component of transportation impact studies for development projects. It ensures that any increased traffic resulting from new development does not unduly burden local residential streets or compromise the safety and quality of life for neighborhood residents. Through careful analysis, data collection, and the implementation of appropriate mitigation strategies, the city aims to protect residential areas from adverse transportation impacts while accommodating new growth and development.

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