# Presentation: 802348

## Low Cost Safety Improvements Pooled Fund Study

- Advanced Street Name Signs

**Dr. James Jenness, Westat**

**Notes:**
Cover page pictures. Picture shows series of three scenarios: a vehicle on a meandering road, safety personnel at work, and a car that is very badly damaged after it appears to have collided into a telephone pole.  

## Overview

- Background
- Status of Data Collection
- Study Design
- Remaining Data Needs
- Evaluation Considerations

##  Background 

- Ranked 14th
- NCHRP Report 500 Series Older Driver Guidebook
- Older drivers are more involved in intersection crashes than other drivers
- Older drivers exhibit excessive vehicle-braking at/before intersections

*Provide advance guide signs and street name signs*

- Photo Source: NCHRP Report 500 Series Volume 9

**Notes:**
Picture: Picture shows the cover page of NCHRP Report 500 Series Older Driver Guidebook

Notes: 
Scenario: Rear-end collisions at or prior to intersections involving older drivers or other crashes involving driver confusion at an intersection (such as stopping a turn midstream).
Questions:
What percentage of intersection crashes are read-end crashes on the approach?
What percentage of those are older driver crashes?
What percentage of intersection crashes are from driver confusion about the intersection?
What percentage of those are older driver crashes?
Information from Older Driver Guide (1997 NHTSA data):
Older drivers exhibit excessive vehicle-breaking at/before intersections.
Older drivers more likely to be in intersection crashes, especially left-turn maneuvers.  
Drivers 85 and older are more than 10 times as likely as 40-49 age group to be in fatal multiple-vehicle crashes at intersections.
More likely to be involved in angle crashes (left turn).
2004 Traffic Safety Facts:
26 million people 70 and older
141,000 injuries 
5,062 (12 percent) of all traffic fatalities are older drivers 
Older drivers’ need for more advance notice at intersections regarding upcoming cross-streets cited in focus groups.  
FHWA is currently funding demonstration projects to evaluate its effectiveness in Washington, Arizona, and Massachusetts.  It may involve components from other strategies. 
Consistent signing across jurisdictions also important.
Older drivers need greater legibility. 

##  Background 

- Tried, low cost, short-term implementation
- Target crashes
- All intersection related
- Rear-end
- Late lane changes
- Night
- Older drivers
- Consistent signing across jurisdictions also important

*Provide advance guide signs and street name signs*

- Photo Source: NCHRP Report 500 Series Volume 9

**Notes:**
Picture: Picture shows an example of advance street name sign. It is a rectangle with green background and inscription written in white

## Background

- Differing methods to provide street names in advance of intersection:

- Photo source: NCHRP Report 500 Series Volume 9 and North Carolina Dept of Transportation (http://www.ncdot.org/doh/preconstruct/traffic/ECHS/groups/docs/int/Advance.pdf)

- Green and white Advance Street Name signs

- MUTCD W3-3 advance traffic control signs with W16-8 supplemental warning plaques

**Notes:**
Picture (top): Picture shows an example of advance street name sign. It is a rectangle with green background and inscription written in white
Picture (below): Picture of Advance Traffic Control Sign W3-3 (traffic light icon) with a supplemental street name plaque below. The plaque is a rectangle with yellow background and inscription written in black.  

Notes: 
The supplemental plaque may be mounted above or below. This is used where there is limited sight distance. Sometimes the supplemental street name plaque is installed at a different time than the Advance Traffic Control Sign.

## Data Collection

**Notes:**
Figure: Shows 50 States of America with Massachusetts and North Carolina, shaded pink to indicate data were obtained from these States.

## Status of Data Collection 

- Massachusetts
- Blanketed strategy across four districts in 2004
- 200 sites included in the study
- Over 400 installed
- Lack of ADT data limited sample

- Limited crash data 2002-2005
- 500 intersection-years of before crash data
- 250 intersection-years of after crash data

**Notes:**
Picture: Picture shows an example of advance street name sign. It is a rectangle with green background and inscription written in white

Notes: 
MA – signs were installed at 400 sites, but due to unavailability of traffic volume data only 200 sites were included in the study. MA uses green signs with while lettering 

A large majority of the MA sites (129 out of 198) have only one count in the major and no counts in the minor.  There are only 16 sites that have a minor count.
There are 502 intersection-years of before crash data.  
There are 251 intersection-years of after crash data. 

NOTE: The strategies implemented in MA and in NC are not directly comparable.  See previous slide.

## Status of Data Collection 

- Crash data from 1997-2004
- 400 intersection-years of before crash data
- 300 intersection-years of after crash data

- North Carolina
- Blanketed strategy in Cary, NC in 2001
- 100 sites included in the study

**Notes:**
Picture (below): Picture of Advance Traffic Control Sign W3-3 (traffic light icon) with a supplemental street name plaque below. The plaque is a rectangle with yellow background and inscription written in black. 

Notes: 
NC – based on previous communications, we should be able to get multiple years of before and after major and minor ADT data for all of the sites.   
There are 400 intersection-years of before crash data.  
There are 300 intersection-years of after crash data. 

NOTE: The strategies implemented in MA and in NC are not directly comparable.  See previous slide.

## Study Design 

- Required Sample Size
- Minimum: 803 intersection-years per period
- Detect a 5 percent reduction in total crashes with 95 percent confidence
- Desirable: 2,031 intersection-years per period
- Detect a 10 percent reduction in older driver crashes with 95 percent confidence

## Study Design 

- Assumptions
- 7.0 crashes per intersection per year in the before period, of which 9 percent involve older drivers
- Crash rate based on preliminary data from MA sites, older-driver share based on Toronto data
- Before and after periods are of equal length
- Equal number of intersection-years for treatment and reference sites

## Remaining Data Needs 

- Minimum: Need 450 more after intersection-years
- Desirable: Need  1,130 before intersection- years and 1680 after intersection-years for older driver
- Need additional installations

**Notes:**
Between MA and NC have 900 before intersection-years and 350 after intersection-years 
Minimum: 803 intersection-years (Before – okay / After 800-350=450 more after intersection years) 
Desirable: 2,031 intersection years (Before 2030–900=1,130 more before intersection years 

## Evaluation Considerations 

- Do not have large enough sample size
- Comparing two methods of signing
- Limited ADT data in Massachusetts

## 				
			Questions? 

- 			Questions?