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Access Management: Why And How? An Introduction To Access Management Problems, Principles and Treatments.

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Presentation on theme: "Access Management: Why And How? An Introduction To Access Management Problems, Principles and Treatments."— Presentation transcript:

1 Access Management: Why And How? An Introduction To Access Management Problems, Principles and Treatments

2 Presentation Outline What is access management? Metro Des Moines access management problems An example corridor: 14 th Street (US 69) Benefits of managing access “Mixes of fixes” for access management Access management, business vitality, and land development Accomplishing better access management

3 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.

4 An Access Management Problem All this commotion was caused by a motorist trying to turn left into a small shopping center Can you provide too much direct land access from an arterial street? ABSOLUTELY!

5 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

6 Access Management Problem Corridors—Des Moines Metro

7 Examples Of Poor Access Management: 14 th Street (US 69)

8 NE 14 th Access-Related Crashes

9 SE 14 th Access-Related Crashes

10 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

11 Operations: Capacity Is Higher On Better Managed Roads

12 Operations: Travel Speed Is Higher On Better Managed Roads

13 Safety: Accident Rates Are Lower On Better Managed Roads

14 Safety: Iowa Case Studies Seven Iowa case studies Case studies show nearly a 40 percent average reduction in crash rates after access management projects were completed.

15 Safety: Crash Reduction By Type After Access Management For Iowa Case Studies

16 Access Management Treatments Help Pedestrians, Too

17 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

18 Conflict Points at Driveways

19 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

20 Separating Conflict Points

21 Facilitating Turning Movements: Important Strategies Fewer, Better Driveways Are Better Than More Driveways Ways 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

22 Steep Driveways Mean Slower Turns Out Or In

23 Dedicated Left And Right Turn Lanes Channelization goes hand in hand with good access management.

24 “Mixes Of Fixes”: Common Access Management Treatments Driveway consolidation Corner clearance Alternative access ways (including internal site design) Continuous two-way left-turn lanes (TWLTL) Medians at intersections Full raised medians We often use combinations of these to manage access

25 Driveway Spacing And Corner Clearance

26 Green Book: functional area of the intersection

27 Too Many Driveways!

28 Good Corner Clearance: University Avenue: Windsor Heights

29 Alternative Access Ways


31 Alternative Access Ways: South Ames

32 Two-Way Left Turn Lane (TWLTL)

33 TWLTL: 3 And 5 Lane Cross-Sections

34 Median At Intersection


36 Full Raised Median

37 Raised Median: 100 th Street Clive

38 Raised Medians Are Very Effective Safety Devices Both of these are a big improvement over an undivided 4 lane

39 Access Management And Business Vitality: Business owners often oppose access changes or restrictions—especially raised medians But measured impacts on businesses and land development are neutral to positive Iowa 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

40 Business Surveys Indicate Neutral- Positive Impact On Business Sales 86% of businesses along newly access managed routes in Iowa reported similar or increased sales

41 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.

42 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

43 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

44 Access Management Can Be Implemented Many Ways When designing new roadways, through good design and the acquisition of access rights When rebuilding roadways When 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

45 Poor Land Use Planning Leads To Access Management Problems: Twin Cities, Minnesota New city park blocks alternative access road route Warehouse where backage road could be

46 Access Management Problems Happen In Rural Areas, Too Areas of concern

47 And Land Use Decisions Can Make Problems Worse

48 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

49 Who Wins When Access Is Properly Managed? Motorists Pedestrians Citizens/taxpayers Businesspersons and developers, for the most part


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