Instructions Text

​Warning Sign Placement Calculator

This module calculates the distance to locate a warning sign in advance of an unexpected traffic condition, such as (but not limited to) a lower speed limit, lane merge, curve, or intersection traffic control.
"Warning signs alert road users to conditions that might call for a reduction of speed or an action in the interest of safety and efficient traffic operations." – MUTCD 2009, Section 2C.01
"The use of warning signs shall be based on an engineering study or an engineering judgment." – MUTCD 2009, Section 2C.02
 NOTE - If an interim intersection or condition exists between the warning signs and its intended condition, add a supplementary plate under the warning sign showing the distance to the intended condition.
  1. Select the POSTED SPEED LIMIT from the drop-down menu
  2. Select the unexpected traffic CONDITION from the three toggle buttons
    1. Speed reduction and lane-changing in heavy traffic This condition is when a motorist must make a judgment in driving, such as a merge point or a lane drop, especially in areas of high traffic volumes. Examples include: Merge, Added Lane, Pavement Width Transition, Right Lane Ends, Left Land Ends, Road Narrows, Narrow Bridge, One-Lane Bridge
    2. Potential Stop Condition This condition is when a motorist may need to stop unexpectedly, such as for intersection cross traffic, pedestrians, or for intersection control. Examples include: Cross road, Side Road, T-intersection, Y-intersection, STOP Ahead, YIELD Ahead, Signal Ahead, Advance Crossing, Limited Sight Distance, Playground
    3. Deceleration Condition This condition is when a motorist will need to reduce speed due to a change in the condition or alignment of the pavement, such as a sharp curve, a bump in the road, or a transition from pavement to dirt. Examples include: Turn, Curve, Reverse Curve, Winding Road, Divided Highway, Divided Highway Ends, Two-Way Traffic, Hill, Bump, Dip, Pavement Ends, and Slippery When Wet
  3. If 'Deceleration Condition' was selected in Step 2, select the lower SPEED LIMIT from the drop-down menu
  4. Press the "Calculate" button
  5. The distance from the warning sign to the unexpected traffic condition is given in the white box labeled "Warning Sign Placement Distance"
  6. To remove all entries and calculations, click the "Reset" button.

Passing Sight Distance Calculator

This module calculates the required minimum passing sight distance for a single passenger vehicle overtaking another passenger vehicle based on the design of a roadway. Passing sight distance refers to the distance required by a typical driver to begin and complete a passing maneuver of a slower vehicle on a two-lane roadway.  An area of roadway cannot be marked as a passing zone (single broken yellow line) unless the minimum passing sight distance is available.
  1. Select the design speed of the roadway from the first drop-down menu.
    • If the design speed is not known, use the posted speed limit plus up to 10 additional mph.
  2. Press the “Calculate” button.
  3. The required passing sight distance will be displayed in the white box.
  4. To remove all entries and calculations, click the “Reset” button.
Notes from AASHTO:

"The passing sight distances shown . . . are sufficient for a single or isolated pass only."

"The passing sight distance for use in design should be based on a single passenger vehicle passing a single passenger vehicle."

"Research has shown that longer sight distances are often needed for passing maneuvers when the passed vehicle, the passing vehicle, or both are trucks."