Where traffic in both directions must, for limited distance, use a single lane in an alternating fashion, some means of coordinating movements at each end shall be used to avoid head-on conflicts and to minimize delays.
Alternate one-way traffic control may be accomplished by single flagger control, multiple flagger control, flag transfer, a pilot car, or by stop or yield control. "Flagger Ahead" signs shall be included in the advance warning area whenever flaggers are present. All flaggers shall be properly trained, attired, and equipped (see Section 15). "One Lane Road Ahead" signs shall be placed in the advance warning area of all one-lane, two-way traffic zones.
At "spot" obstructions (such as an isolated pavement patch or pipe crossing) on minor roadways with low speeds and very low volumes and with adequate sight distance, the movement may be self-regulating and no control is necessary.
A. SINGLE FLAGGER METHOD
Where a one-lane, two-way TTC zone is short enough to allow visibility from one end to the other, and traffic volumes and speeds are moderate to low, traffic may be controlled by a single flagger. The flagger should be stationed on the shoulder opposite the workspace, or in a position where good visibility and traffic control can be maintained at all times.
B. MULTIPLE FLAGGERS
When good visibility and traffic control cannot be maintained by a single flagger, traffic should be controlled by a flagger on each end of the work area. One of the flaggers should be designated as the coordinator. The flaggers should be able to communicate with each other orally or with signals. Signals should not be able to be mistaken with flagging signals to traffic. The use of radios is recommended even when there is visual contact between the flaggers.
Multiple flaggers are likely to be needed on streets with higher traffic volumes and higher speeds and where the site conditions limit the visibility of a single flagger to approaching traffic. In TTC zones at intersections, it may be necessary to post flaggers on the intersecting streets to avoid conflicts with vehicles approaching the site from these streets.
C. FLAG TRANSFER METHOD
The flag transfer method can be very effective for long one-lane, two-way TTC zones; especially when flaggers are not able to see one another. This method requires proper flagging operations at each end of the constricted area. Flaggers must also be stationed at each intersecting street or the intersecting streets must be closed.
D. PILOT CAR METHOD
A pilot car is used to guide a queue of vehicles through a complex or very long one-lane, two-way TTC zone. Its operation must be coordinated with flagging operations at each end of the one-lane section. Flaggers must also be stationed at each intersecting street or the intersecting streets must be closed.
Pilot cars shall have the PILOT CAR sign (G20-4) mounted at a conspicuous location on the rear of the vehicle.
The pilot car method will not generally be used under the urban conditions to which this handbook applies. This method is offered as an acceptable alternative and may be useful in helping to control speeds through TTC zone, even when two-way traffic is maintained.
E. STOP OR YIELD CONTROL
On low volume, low speed roadways where the TTC zone is very short and there is excellent visibility of the entire work zone to approaching traffic, a Yield (R1-2) or Stop (R1-1) sign may be used to control traffic. If the STOP or YIELD sign is installed for only one direction, then the STOP or YIELD sign should face users who are driving on the side of the roadway that is closed for the work activity area.