4.10.5 Pavement Taper Lengths

The following equations define minimum taper lengths where lanes and/or shoulders are reduced, opened, or shifted.
These equations define minimum taper lengths.
The project conditions (e.g., higher traffic or truck volumes) may indicate the need for additional lengths or appropriate horizontal curvature. For guidance on the length of tapers for turn lanes, acceleration lanes, or deceleration lanes, see
Table 4-14
.
L = WS
, for S ≥ 45 mph
L = WS²
 / 60, for S < 45 mph
Where:
L =
 Length of taper, ft
W =
 Width of offset, ft
S =
 Posted speed, mph
When more space is available, a longer than minimum taper distance can be beneficial.
4.10.5.1 Lane Reduction Transition Taper (L)
Lane-reduction transition tapers are used where the number of through travel lanes is reduced due to narrowing of the roadway or section of on-street parking.
The minimum length of a lane reduction transition taper is L.
4.10.5.2 Approach Taper for Obstructions (L)
Approach tapers for obstructions are used where the width of a through travel lane is reduced because of a fixed obstruction within a paved roadway. An approach taper for an obstruction is required upstream and downstream of the obstruction.
The minimum length of an approach taper for obstruction is L.
4.10.5.3 Lane-Opening Taper (½ L)
Lane-opening tapers are used where a through travel lane is added without a lateral shift of the through traffic.
The minimum length of a lane-opening taper is ½ L.
4.10.5.4 Shoulder Taper (1/3 L)
Shoulder tapers are used where the improved shoulders are reduced or increased in width.
The minimum length of a shoulder taper is 1/3 L.
Note that near the respective project termini, due to site conditions such as tying into to existing grading, drainage constraints, other site-specific circumstances or planned future project tie ins, there may be a reduction in the available length of taper (a design waiver is not required). In such circumstances an emphasis should be placed on the correct placement of pavement markings and signage indicating a reduction or elimination of the shoulder, in accordance with the
Texas Manual on Uniform Traffic Control Devices (TMUTCD)
and applicable Traffic standards.
4.10.5.5 Shifting Taper
Shifting tapers are used to perform a lateral shift of the through traffic during temporary traffic control activities (i.e., construction, maintenance, and incident management). Shifting tapers should not be used to address permanent changes in horizontal alignment. When a change in horizontal alignment is required, the design criteria from
Chapter 4
should be used.
For additional information on temporary traffic control refer to the
TMUTCD
.