Delaware Administrative Code
Title 2 - Transportation
2000 - Department of Transportation
2400 - Division of Transportation Solutions
2402 - Manual on Uniform Traffic Control Devices (MUTCD)
Part 6 - Temporary Traffic Control
Chapter 6C - TEMPORARY TRAFFIC CONTROL ELEMENTS
Section 6C.08 - Tapers
Current through Register Vol. 28, No. 3, September 1, 2024
Option:
01 Tapers may be used in both the transition and termination areas. Whenever tapers are to be used in close proximity to an interchange ramp, crossroads, curves, or other influencing factors, the length of the tapers may be adjusted.
Support:
02 Tapers are created by using a series of channelizing devices and/or pavement markings to move traffic out of or into the normal path. Types of tapers are shown in Figure 6C-2.
03 Longer tapers are not necessarily better than shorter tapers (particularly in urban areas with characteristics such as short block lengths or driveways) because extended tapers tend to encourage sluggish operation and to encourage drivers to delay lane changes unnecessarily. The test concerning adequate lengths of tapers involves observation of driver performance after TTC plans are put into effect.
Guidance:
04 The appropriate taper length (L) should be determined using the criteria shown in Tables 6C-3 and 6C-4.
05 The maximum distance in feet between devices in a taper should not exceed 1.0 times the speed limit in mph.
Support:
06 A merging taper requires the longest distance because drivers are required to merge into common road space.
Guidance:
07 A merging taper should be long enough to enable merging drivers to have adequate advance warning and sufficient length to adjust their speeds and merge into an adjacent lane before the downstream end of the transition.
| Table 6C-3. Taper Length Criteria for Temporary Traffic Control Zones (Delaware Revision) | |||
| Type of Taper | Taper Length | ||
| Merging Taper | at least L | ||
| Shifting Taper | 0.5 L to L* | ||
| Shoulder Taper | at least 0.33 L | ||
| One-Lane, Two-Way Traffic Taper | 50 feet minimum, 100 feet maximum | ||
| Downstream Taper | 50 feet minimum, 100 feet maximum | ||
| Note: Use Table 6C-4 to calculate L * A shifting taper length of L is preferred on state-maintained roads | |||
| Table 6C-4. Formulas for Determining Taper Length (Delaware Revision) | |||||||
| Speed (S) | Taper Length (L) in feet | ||||||
| 40 mph or less | L = | WS2 | |||||
| 60 | |||||||
| More than 40 mph | L = | WS | |||||
| Where: L WS | = taper length in feet = width of offset in feet = posted speed limit, or off-peak 85th-percentile speed prior to work starting, or the anticipated operating speed in mph | ||||||
Support:
08 (DE Revision) A shifting taper is used when a lateral shift is needed. When more space is available, a longer than minimum taper distance can be beneficial. Changes in alignment can also be accomplished by using horizontal curves designed for normal highway speeds in accordance with the DelDOT Road Design Manual.
Guidance:
09 (DE Revision) A shifting taper length of L is preferred on state-maintained roads (see Tables 6C-3 and 6C-4).
Support:
10 A shoulder taper might be beneficial on a high-speed roadway where shoulders are part of the activity area and are closed, or when improved shoulders might be mistaken as a driving lane. In these instances, the same type, but abbreviated, closure procedures used on a normal portion of the roadway can be used.
Guidance:
11 If used, shoulder tapers should have a length of approximately 1/3 L (see Tables 6C-3 and 6C-4). If a shoulder is used as a travel lane, either through practice or during a TTC activity, a normal merging or shifting taper should be used.
Support:
12 A downstream taper might be useful in termination areas to provide a visual cue to the driver that access is available back into the original lane or path that was closed.
Guidance:
13 If used, a downstream taper should have a minimum length of 50 feet and a maximum length of 100 feet with devices placed at a spacing of approximately 20 feet.
Support:
14 The one-lane, two-way taper is used in advance of an activity area that occupies part of a two-way roadway in such a way that a portion of the road is used alternately by traffic in each direction.
Guidance:
15 Traffic should be controlled by a flagger or temporary traffic control signal (if sight distance is limited), or a STOP or YIELD sign. A short taper having a minimum length of 50 feet and a maximum length of 100 feet with channelizing devices at approximately 20-foot spacing should be used to guide traffic into the one-lane section, and a downstream taper should be used to guide traffic back into their original lane.
Support:
16 An example of a one-lane, two-way traffic taper is shown in Figure 6C-3.
