Access Management: Why And How?
An Introduction To Access Management Problems, Principles and Treatments
Presentation Outline
What is access management?Metro Des Moines access management problemsAn example corridor: 14th Street (US 69)Benefits of managing access“Mixes of fixes” for access managementAccess management, business vitality, and land developmentAccomplishing better access management
What Is Access Management?
Providing adequate access to land development while simultaneously preserving the safe and efficient flow of traffic on the surrounding road system.In other words, a balancing act.
An Access Management Problem
All this commotionwas caused by a motoristtrying to turn leftinto a small shoppingcenter
Can you provide toomuch direct landaccess from anarterial street?
ABSOLUTELY!
Costs Of Not Managing Access
What happens when we fail to do a good job of managing access? Certain types of crashes happen more
frequently Rear-end, left-turn, right turn
Mean travel speeds drop; LOS drops The investment the public has made
in roadways is degraded
Access Management Problem Corridors—Des Moines Metro
Examples Of Poor Access Management: 14th Street (US 69)
NE 14th Access-Related Crashes
SE 14th Access-Related Crashes
What Are The Benefits of Managing Access?
• Improved traffic flow• Improved traffic level of service• Preservation of investments in capacity• Higher mean travel speed on arterials
• Lower crash rates• Poorly-managed roads are 40 to 50
percent less safe• Pedestrian safety can also be improved
Operations: Capacity Is Higher On Better Managed Roads
Operations: Travel Speed Is Higher On Better Managed
Roads
Safety: Accident Rates Are Lower On Better Managed Roads
Safety: Iowa Case Studies
Seven Iowa case studiesCase studies show nearly a 40 percent average reduction in crash rates after access management projects were completed.
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1
2
3
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Crash Rate
(per MVMT)
Before
After
Safety: Crash Reduction By TypeAfter Access Management
For Iowa Case Studies
0 50 100 150 200 250
Rear End
Left/Broadside
Right Angle
Other
Total
Before
After
Access Management Treatments Help Pedestrians, Too
Access Management Basics
Limit conflict points Separate conflict points Remove turning traffic from through
traffic lanes through channelization Reduce speed differential
Facilitate faster left and right turns
Conflict Points at Driveways
Separating Conflict Points: Why?
Conflict points represent opportunities for crashes, congestion, and delay
Drivers can only mentally process one conflict point at a time
Separation provides more time and space for drivers to react to the unexpected
Conflict points and other poor access features increase speed differential between through and turning traffic
Speed differential = Speed of fastest traffic – speed of slowest traffic
Greater speed differential generates more rear end collisions
Separating Conflict Points
Facilitating Turning Movements: Important Strategies
Fewer, Better Driveways Are Better Than More DrivewaysWays To Improve Driveways Increase the turning radius Increase driveway width Decrease driveway slope Include dedicated turn lanes or tapers Improve sight distance for turning traffic Provide opportunities for internal circulation within
developments
Provide dedicated turn lanes where warranted
Steep Driveways Mean Slower Turns Out Or In
Dedicated Left And Right Turn Lanes
Channelization goes hand in hand withgood access management.
“Mixes Of Fixes”:Common Access Management
Treatments
Driveway consolidationCorner clearanceAlternative access ways (including internal site design)Continuous two-way left-turn lanes (TWLTL)Medians at intersectionsFull raised mediansWe often use combinations of these to manage access
Driveway Spacing And Corner Clearance
Green Book: functional area of the intersection
Too Many Driveways!
Good Corner Clearance: University Avenue: Windsor Heights
Alternative Access Ways
Alternative Access Ways
Alternative Access Ways: South Ames
Two-Way Left Turn Lane (TWLTL)
TWLTL: 3 And 5 Lane Cross-Sections
Median At Intersection
Median At Intersection
Full Raised Median
Raised Median: 100th Street Clive
Raised Medians Are Very Effective Safety Devices
Both of theseare a big improvementover anundivided 4lane
Access Management And Business Vitality:
Business owners often oppose access changes or restrictions—especially raised mediansBut measured impacts on businesses and land development are neutral to positiveIowa study results after access management show: Retail sales levels often improved Business turnover rates did not increase No impact on commercial land values A few individual businesses thought they were
negatively affected
Business Surveys Indicate Neutral-Positive Impact On Business Sales
Decreased
5%
Same
53%
Increased
33%
Uncertain
9%
86% of businessesalong newlyaccess managedroutes in Iowareported similar or increasedsales
Businesses Choose Locations Based On Where Their Potential Customers Are
Businesses locate on poor and better managed routes…small changes in access do not seem to matter much.
A Must In Access Management
To have a successful access management program, you have to work closely with business and land owners and educate them
Implementing Access Management
In Iowa, roadway jurisdictions are legally responsible for managing access and for providing access to properties.State legislation governing access in Iowa is open to interpretation:
Roadway jurisdictions must provide “reasonable access”
This has been taken to mean that access to roadways does not have to be direct access
It has also been taken to mean that roadway jurisdictions have the right to install raised medians even if they diminish businesses’ access to traffic flow in one direction
Access Management Can Be Implemented Many Ways
When designing new roadways, through good design and the acquisition of access rightsWhen rebuilding roadwaysWhen permitting driveways on roadways Prior to new development Prior to expanded development
When regulating land use In subdivision regulations, such as driveway
spacing, indirect access from arterials, or joint or cross access regulations
When applying zoning along arterials
Poor Land Use Planning Leads To Access Management Problems: Twin Cities, Minnesota
New city park blocks alternative New city park blocks alternative access road routeaccess road route
Warehouse where backageWarehouse where backageroad could beroad could be
Access Management Problems Happen In Rural Areas, Too
Areas of concern
And Land Use Decisions Can Make Problems Worse
Implementing Access Management Is A “Team
Sport”
Good Access Management Results Depend On The Involvement Of: All government agencies involved Adjacent business owners Land developers The public, including motorists and
pedestrians
Who Wins When Access Is Properly Managed?
MotoristsPedestriansCitizens/taxpayersBusinesspersons and developers, for the most part