Geometric Design & Layout Development
Layouts and Checklists
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The information contained in a completed layout is not only needed by Geometrics in order to do a quality job reviewing a project but is needed by the various work units within MnDOT in order to get the project constructed efficiently. The layout is viewed and used by the rest of our customers, including the public. The layout becomes the best and most useful drawing we have picturing the project. Layouts need to be prepared with all customers in mind. A project manager needs a good graphics product that is easy for the public to understand and also help him sell good ideas. We all need detailed information and research to help make choices and lay a basis for further project development. The layout becomes a historic document and is used for future reference.

 

This checklist contains items considered important features of a completed layout. The items deal with attachments, base map features, design geometrics and profiles. This checklist will be used as a review tool to improve layout quality and its content.

 

ATTACHMENTS OR LAYOUT MANAGEMENT

 

SUBMITTAL LETTER:

General location description and request for staff approval or review gives explanations and reasons for design choices and areas of compromise, background data on existing road which are not evident in layout (examples provided upon request) provided even if no Level 1 involvement.

 

TITLE BLOCK:

Proper project description, limits, T numbers, layout date, layout scale, year of traffic volumes, name of project manager and layout technician or consultant who prepared layout

 

INDEX MAP:

A legible map defining roadways, cities and counties and other major features in the project area.

 

HISTORY:

Geometric history could begin with concepts and continue through layout approval using layout number or concept name and date to describe geometric and development changes. Document the geometric decisions made, explain alternate proposals studied. Keep current with every layout issue- examples provided upon request.

 

APPROVAL BLOCK:

Applicable department block with dated signatures.

 

 

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RESEARCH AND BASE MAP

 

A good base map along with complete research is essential in providing a complete picture. The people viewing and using the layouts are not all experts or technical personnel and they need and expect maps to be clearly defined. Also many work units use layout information for guidance and these checklist items are therefore helpful to many.

 

BASIC TOPOGRAPHY:

Show all highways, streets, all surface waterways, bridges, railroads, major known utilities, buildings, entrances, in place geometrics, boundaries- for printing, graphically set existing topography a lighter weight than proposed design. Map should run left to right-west to east-south to north- with stationing.

 

MAJOR UTLITIES:

Above and below ground utilities in project area. Place approximate if needed with note. Utilities that would encompass major project change Examples include high voltage overhead power lines, sanitary force mains, natural gas pipelines, etc.

 

CITY/COUNTY LIMITS:

Limits to be shown even if labeled “approximate” to define city or county involvement and to determine municipal approval. County name could be labeled on base map or index map.

 

NORTH ARROW:

Repeated enough to eliminate questions.

 

EXISTING SPEEDS ZONES:

Label existing speeds limits on layout and limits of change. This helps formulate geometric decisions.

 

TRAFFIC DATA:

Displayed researched traffic volumes, turning movement counts, projected data, and if possible heavy commercial counts. Assemble on layout in charts or other easily understood form. This is important for traffic engineering, design evaluation and capacity needs.

 

IN PLACE SIGNALS:

Show location with proper symbol and label.

 

RIGHT OF WAY:

Show the right of way limits for roadways and railroads, in addition to access control. Use symbols shown in Technical Manual and label “approximate” if necessary. Show property lines if in a critical area.

 

IN PLACE RD. STATIONS:

Use good labels, transition to and from new alignments. Useful when referring to existing road and bridge plans.

 

IN PLACE ALIGNMENTS:

Use good labels. Alignments are useful when referring to existing road and bridges conditions and plans.

 

 

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RAILROADS:

Located graphically and labeled with ownership. Show their right of way and number of tracks.

 

WATERWAYS:

Limits located and labeled, desirable to show in a color.

 

LAYOUT SCALE:

Use 1″=100 feet. 1″=50 feet is desirable on smaller project layouts and useful for blow ups of critical areas. Show a bar scale with map legend.

 

INPLACE WIDTHS:

In place turn lanes, shoulders, raised median, streets, lane, and entrance widths in addition to other important dimensions help formulate geometric choices. Show when practical and pertinent to the design.

 

BRIDGE NUMBERS:

Place label on all existing bridges within the project area.

 

ENTRANCES:

Show as accurately as possible all in place and future. Field review project for new entrances. Check on new and future land developments.

 

ROADWAY NAMES:

Easy to read and complete labels. Use large font, as the layout is used for display as in a meeting.

 

LAND USE:

Indicate how land/lots are being used, including “unknown white areas” shown on base maps which could be affected by project.

 

SENSITIVE AREAS:

Show all areas defined as archaeological sites, environmentally sensitive areas, cemeteries, parks, airports, etc.

 

BUSINESS NAMES:

This indicates how site is used relative to vehicle type and entrance needs, in addition to identifying the property owner. It is very useful at public meetings to identify access.

 

ADDRESSES:

This is useful in identifying property owner in reference to map, and especially helpful when fielding phone calls and at meetings. It ties structures to base map location.

 

TRUCK USAGE:

If available show truck counts or any indication of truck usage of roadway, entrance or cross street. Data helps determine corner radii needs, turn lane storage length and construction materials.

 

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INPLACE TYPICALS:

Helps everyone understand the current geometry representative for roadways, ramps, bridges and other special features show typical relative to layout direction.

 

DESIGN

 

PROPOSED SIGNALS:

Use symbol and color code to designate location along with a bold label. Show only if traffic engineer agrees to installation.

 

TRANSIT ITEMS:

Show any HOV bypass, bus stops, bus turnouts or pads, park and ride lots, special lanes and other transit details.

 

RAMP METERS:

Proposed location and label.

 

WIDTHS:

Show all proposed widths for bypass lanes, truck climbing lanes, auxiliary lanes, turn lanes, HOV lanes, shoulders, medians, bridge features, walks, trails, entrances, etc.

 

COLOR CODING:

A good use of color should be used to represent geometric and other features. Use standard colors shown in the MnDOT cell library and use map legend.

 

LANE NAMES:

Label all types of lanes: bypass, turns lanes, and auxiliary.

 

LANE LENGTH:

Show length of special lanes without including taper length.

 

PROP. RIGHT OF WAY:

Show the approximate right of way needs and access control with proper symbols. Also consider showing “total takes”.

 

PRELIMINARY CONSTRUCTION LIMITS:

It is desirable, but not required, to have approximate construction limits shown on layout especially in all close fitting and sensitive areas. Where construction limits have not been completed, the designer needs to have done adequate study that plan features are feasible with constraints.

 

SIGHT CORNERS:

Where appropriate show minimum sight corners as outlined in the Road Design Manual.

 

PROP. ENTRANCES:

Show the perpetuation, relocation and closing of entrances and public roadways. Dimension entrances if possible, especially if new or modified.

 

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CLOSURES:

Show distinctly and label closures of roads and entrances.

 

ENTRANCE WIDTHS:

Dimension if possible, especially if new or modified.

 

TAPERS:

1:15, 1:50 – label distinctly. A “1:speed taper” is preferred for driver’s mainline lateral movement- 1:15 is a standard taper for turn lanes, and should be sharper on the inside or outside of a curve. Use tic marks to define taper ends.

 

RADII:

Label all radii; indicate endpoint with tic marks. On alignment curves, show the PC and PT with alignment point circles.

 

VEHICLE TURN PATH:

A graphic simulation showing the wheel path used by the design vehicle or vehicles to negotiate proposed intersection geometry.

 

RETAINING WALLS:

Show in appropriate dimension and color, and indicate approximate heights. Take note of space necessary to place footings or use of sheeting when figuring construction limit.

 

TRAFFIC ARROWS:

Very visible directional arrows can enhance drawing and eliminate confusion, especially for the public.

 

PONDS:

Show approximate location and limits, enhance with color.

 

TYPICAL SECTIONS:

Show representative geometrics for proposed roadways, ramps and other special features. This is sometimes the first shot at getting a reaction from customers for intended widths, slopes, and offsets. The typical should face the same direction as layout.

 

BRIDGE NUMBERS:

The new bridge number for the proposed structure should be labeled.

 

BRIDGE TYPICALS:

Show representative geometrics for bridges and other special features. This is sometimes the first shot at getting a reaction from customers for intended widths, slopes and offsets. The typical should face the same direction as layout.

 

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MINIMUM SIGHT DISTANCE:

Horizontal, intersection and 10-second decision sight distance should be checked, noted and shown where of interest.

 

LAYOUT NOTES:

Add notes on the layout that clarify construction, land use, proposed land use and important items that otherwise are not readily evident on the layout.

 

PLOT NAME AND DATE:

Layouts that are prepared on CADD should have file name and date of plot shown on layout.

 

PROP. STATIONING:

New centerline alignments should be stationed with ties to in place stationing. Use of equations where appropriate, ramps should have some logical tie to the mainline. Intersecting alignments could be identified. Numbers should be easy to read.

 

PROP. ALIGNMENTS:

Used to describe new centerlines, use alignment point circles to identify alignment changes. Roadways with center medians should have separate alignment for each direction to demonstrate they are properly aligned.

 

PROP. DESIGN SPEED

Given the horizontal and vertical alignment restrictions show the proposed design speed and location where it changes.

 

PEDESTRIAN ACCOMODATIONS:

Show walk and trail proposals, along with widths.

 

CROSSWALKS LOCATION:

Show proposed locations.

 

MINIMUM CLEARANCE:

Dimension to close fixed objects, proposed or in place features. Can be a vertical clearance if no profile is provided. These clearances can relate to other roadways, retaining walls, bridges, bridge piers and abutments, bridge rails, buildings, barriers, etc.

 

DESIGN EXCEPTIONS:

If there is a design exception it needs to be identified on the layout.

 

ROUNDABOUT DATA

 

ROUNDABOUT INSERT:

The roundabout insert will consist of a large scale drawing which shows the roundabout in full detail. The roundabout insert should contain the alignment for the roundabout, entry widths, circulatory roadway width, truck apron width, radii contained throughout the roundabout, curb & gutter designations, inscribed circle diameter, exit widths, and pedestrian accommodations with curb ramps.

 

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ROUNDABOUT TYPICAL:

Show representative geometrics for the proposed roundabout. This is sometimes the first shot at getting a reaction from customers for intended widths, slopes and offsets. The whole typical section does not need to included, it can be shown from the center of the roundabout outwards.

 

VEHICLE PATH RADII:

The five critical path radii shown in exhibit 6-12 of the FHWA “Roundabouts: an Informational Guide” document. These five critical paths should also be shown should also show the achieved speed for all five critical paths.

 

VEHICLE PATH RADII TABLE:

A chart which summarizes the five critical path radii for each entrance to the roundabout and the relative speed differences between R4 and the rest of the radii.

 

PATH OVERLAP DIAGRAM:

A graphical simulation which shows the path overlap for multi-lane roundabouts between the design vehicle in lane one and a passenger vehicle in lane two.

 

PROFILE

 

Develop profile on proposed alignments and name the profile segments consistent with layout. Use profile title block. Designer should review Design Manual relative to the use of broken back curves and the use of “uncomfortable short” vertical curves. Try not to use sharp vertical and horizontal alignment together. Show bridges, equations, develop ground line and ground water elevation when appropriate.

 

VERTICAL CURVE DATA:

Show the length of curve, m distance, K value, stopping sight distance achieved for crests in miles per hour, beginning and end of curves, headlight sight distance achieved for sags in  miles per hour, P.I.’s shown, transitional curves to in place displayed, ends of curves should be show using an alignment point circle.

 

GRADES:

All proposed grades need to be well labeled, preferably on the vertical tangent line. All existing grades should be noted. Existing ground lines shown where appropriate.

 

BEGINNING & END OF PROFILE SEGMENTS:

Identify the touchdown point and ties to existing vertical alignment graphically. Ramp profiles should include a portion of the mainline to show continuity.

 

NOSES:

On freeway designs show ramp noses on mainline profile. This helps determine the profile touchdown and vertical sight distance on mainline and its relative position.

 

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CROSSOVERS:

Identify road overpass or underpass positions, relative to vertical clearance.

 

CROSS STREETS:

All intersection centerlines should be shown and all entrance locations. This is helpful in examining their positions relative to vertical geometry and sight distance.

 

BRIDGES:

All proposed and in place structures should be located. All new construction needs to be colored orange. Identify the minimum vertical clearance and label the bridge numbers.

 

MIN. VERTICAL CLEARANCE:

Show anticipated or existing vertical clearance.

 

DIRECTION OF: TRAVEL:

Show direction of vehicle travel on ramps and one ways with arrows to eliminate confusion when viewing or checking geometry.

 

STOPPING SIGHT DISTANCE:

Show on vertical crests relative to miles per hour to assure proper geometry. K value should be indicated.

 

HEADLIGHT SIGHT DISTANCE:

Label in “miles per hour” on vertical sags, especially in unlit areas, be concerned with comfort range when using short curves.

 

DECISION SIGHT:

We should be concerned with vertical decision sight distance at intersections, ramp terminals, nose and other complicated roadway elements when vertical curvature compromises needed driver information.

 

INTERSECTION SIGHT DISTANCE:

Identify that adequate safe maneuvering sight distance is provided for approaching or entering vehicle operators.

 

PASSING SIGHT DISTANCE:

Non-striping sight distance is considered the desirable design for two lane roads and if possible, passing sight distance should be provided. Stopping sight is considered minimum design. These distances should be examined where appropriate and identified.

 

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