Adjusting Speed Limits Jon Cheney, P.E. July 7, 2016

Adjusting Speed Limits Agenda: What Influences Driver Speed? Florida Statute 316.189(2) Florida DOT Criteria How VCTE Handles Speed Request Speed Study Example Staff Recommendations Questions

What Influences Driver Speed? Time of day/purpose of trip Pavement wetness Ambient light Weather Familiarity of driver with the road Type of vehicle Vehicle parking Condition of vehicle Road width Urgency of trip Lane width Emotional condition of driver Traffic volume Driver skill Adjacent land use and development Personality of driver Speed of other vehicles Pavement roughness Driver - late or on time Shoulder width and condition Presence and/or history of enforcement Pavement type and condition Road geometrics Form Road geometrics    Road width Lane width On street parking Adjacent land use/development Length of trip Activity Traffic volume (Including presence of pedestrians & Bicycles) Florida Department of Transportation

Adjusting Speed Limits Florida Statute 316.189(2) SPEED ON COUNTY ROADS After an investigation determines: - change is reasonable AND - conforms to Florida DOT criteria, then Speed may be set by the County Council

Adjusting Speed Limits Florida DOT Criteria Found in Speed Zoning for Highways, Roads and Streets in Florida, 2010 Investigation determines: - 85th percentile of speed - 10 MPH pace speed May adjust +/- 3 MPH in investigation Adjusting -4 to -8 MPH requires supplemental investigation into: - Roadway Length - Traffic Volume - Alignment - Crash Experience - Roadway Width - Sight Distance - Surface Condition - Design Speed - Development - Speed in Curves

Adjusting Speed Limits HOW VCTE HANDLES SPEED REQUEST Receive Request from Variety of Sources: Residents Businesses Government staff (i.e., city/county/state) Elected officials (i.e., city/county/state/federal) Screen Each Individual Requests No further action-document request, when:  Last speed study performed along roadway w/in past several years  Post speed is same as roadway design speed If law enforcement issue or cut through traffic problem:  Will use radar feedback sign  Will refer them to local law enforcement agency Will perform full Speed Study after:  Field review of roadside development & roadway alignment  Review crash history

Adjusting Speed Limits - Example Residential Local Street ¼ MILE LENGTH Posted Speed – 30 MPH FIELD REVIEW Roadway Alignment: - 2 horizontal curves Roadside Development - Driveway spacing - Parked cars adjacent to road

100% Adjusting Speed Limits - Example FIELD STUDY Frequency Distribution of Spot Speeds 100% Participation by every user driving on the road over 48-hour period Existing Speed Limit – 30 MPH Accident rate is 3x normal rate for this type road NUMBER of VEHICLES VEHICLE SPEED (MPH)

Adjusting Speed Limits - Example Frequency Distribution of Spot Speeds FDOT Criteria Investigation determines: - 10 MPH pace speed Frequency Distribution of Spot Speeds 10 MPH Pace: 15-25 MPH Existing Speed Limit – 30 MPH Accident rate is 3x normal rate for this type road NUMBER of VEHICLES VEHICLE SPEED (MPH)

Adjusting Speed Limits - Example FDOT Criteria Investigation determines: - 85th percentile of speed CONVERT Frequency Distribution of Spot Speeds TO Cumulative Speed Distribution DETERMINE 85th Percentile of Speed 85th %tile Speed: 27.1 MPH CUMULATIVE % FREQUENCY Existing Speed Limit – 30 MPH VEHICLE SPEED (MPH) Cumulative Speed Distribution

Adjusting Speed Limits - Example Cumulative Speed Distribution FDOT Criteria May adjust +/- 3 MPH 85th %tile Speed: 27.1 MPH Upper 10 MPH Pace: 25 MPH +/- 3 MPH: 24-30 MPH CUMULATIVE % FREQUENCY +/- 3 MPH: 22-28 MPH Existing Speed Limit – 30 MPH VEHICLE SPEED (MPH) Cumulative Speed Distribution

Adjusting Speed Limits - Example Cumulative Speed Distribution FDOT Criteria May adjust +/- 3 MPH Potential Speed 20 – 30 MPH +/- 3 MPH: 24-30 MPH CUMULATIVE % FREQUENCY +/- 3 MPH: 22-28 MPH Existing Speed Limit – 30 MPH VEHICLE SPEED (MPH) Cumulative Speed Distribution

Adjusting Speed Limits - Example Cumulative Speed Distribution FDOT Criteria May adjust +/- 3 MPH Potential Speed 20 – 30 MPH Study recommends adjusting speed from 30 mph to 25 mph CUMULATIVE % FREQUENCY Existing Speed Limit – 30 MPH 85th %tile Speed - 27.1 MPH VEHICLE SPEED (MPH) Cumulative Speed Distribution

Adjusting Speed Limits RECOMMENDATIONS: Going to County Council as extra precaution Biannually Consent agenda item Adjusting speeds on ALL road types: - Arterials - Collectors - Local residential streets

QUESTIONS?