Traffic Engineering

Welcome to the Traffic Engineering page! This page presents technical arguments and data in support of policies, research initiatives, and practices advocated by Scott Kuznicki. These technical summaries are being developed to assist the traffic engineering community in identifying practices that are considered particularly important in the interest of promoting uniformtiy, improving safety and operations, and providing for a transportation system that better meets the needs of motorists.

In general, one of the themes that is expressed by this series of technical position papers is the concept of "Use one traffic control device for one scenario and treat all similar scenarios with one traffic control device." Too often, inexperienced traffic engineers will utilize a TCD such as a warning sign in two or three or more locations with dissimilar characterstics. On the other hand, that same traffic engineer is also likely to treat similar situations with differing implemenations of TCDs. Without this "1-to-1" parity of device treatments and field conditions, motorist expectation is severely eroded and the effectiveness of traffic control devices, particularly in crtical situations, is reduced.

ISSUE 1
Properly Distinguishing Short Lane Lines and Dotted Extension Lines

Dotted Extension Lines are intended to separate traffic in transition areas. Typically, this occurs between full-width travel lanes and a tapering, non-full-width portion of an adjacent lane, such as a turn lane taper, lane width reduction taper, or through itnersections. Short Lane Lines, sometimes called "Drop Lines", are intended to separate two full-width lanes, where one lane is non-continuing, such as in the case of a freeway where a mandatory movement lane exists adjacent to a through lane.

ISSUE 6
Signing for Lane Reduction Transitions

The use of the RIGHT LANE ENDS, LANE ENDS MERGE LEFT, and Lane Reduction sybmol signs is inconsistent. The non-uniform placement and use of the lane reduction warning signs, coupled with a pavement marking design that does not facilitate easy identification of the beginning of the lane width reduction taper. Elimination of the confusing LANE ENDS MERGE LEFT sign, introduction of the MERGE sign, and standardized placement of all lane reduction warning signs, will improve the operational efficiency and safety performance of lane reductions on all types of roads. See the proposal here.

ISSUE 17
Guide Signing for Option Lanes on Freeways and Expressways

The provision of overhead guide signing of option lanes applies the arrow theory of Issue 19 to provide clear and consistent signing of optional movement lanes for service interchanges, system interchanges, and major divergences at the termination of shared routes. The use of downward-pointing arrows in advance of and slanted upward-pointing arrows at the ramp terminal of interchanges, in a consistent manner, has been successfuly demonstrated in over 30 states. Download Mr. Kuznicki's 2011 presentation (Micrsoft PowerPoint, 10.51 MB) to the Traffic Control Devices Committee (AHB50) of the Transportation Research Board.

ISSUE 19
Arrow Theory

Use of Type A, Type B, and Down arrows on guide signs must follow several basic principles. Simply, the principles are "Upward and slanted Type A and Type B Arrows indicate departures", "Down Arrows indicate continuing lanes and major movements", and "Downward and slanted Type A and Type B Arrows indicate the marking of traveled ways". These principles can also be applied to Type C and Type D arrows as well.

ISSUE 23
Patterns for Raised Reflective Supplemental Pavement Markings

In Washington State, non-continuing freeway lanes are marked with double reflectors spaced at 15-foot intervals. Edge markings and gore markings use 20-foot and 40-foot intervals, despite the fact that those markings create less of a visual barrier. The correct solution would be to decrease reflector spacing from an 80-foot interval for lane lines to a 20-foot interval for edge lines and gore markings, such that 60-foot and 40-foot spacings indicating increasing degrees of restriction, for the non-continuing lane and the solid lane line, respectively, presented a visual cue that was consistent with the change in lane use control.

ISSUE 42
Solid Lane Line Separators for Through Lanes at Intersections

The use of solid lane lines between through lanes, a common practice in several states, including South Dakota, can create confusion between the continuing lanes and auxiliary/turn lanes of intersections, particularly in locations where traffic signing and geometric design are found to be atypical.