The advanced stop line or "bike box"

An inline bike box is frequently implemented along with a bike lane, as in the photo, so bicyclists have a designated space in which they may overtake stopped traffic.

The inline bike box allows bicyclists to get ahead of the first motorist waiting at a traffic light. On casual observation, it appears to advance the status of bicyclists over that of motorists. Not only do bicyclists get to go to the head of the line but also, motorists must wait in line behind the bicyclists. But there are disadvantages too.

Operational characteristics

Cross-street bike box

The cross-street bike box involves an average wait of 3/4 signal cycle when the bicyclist arrives on the red or 1/4 when the bicyclist arrives on the green, for an average delay of 1/2 signal cycle. In addition, there may be time waiting in queue to enter the intersection and time waiting in the bike box for traffic to clear.

Though the distance traveled is longer than for a vehicular left turn, the total time may be shorter if there is a long queue waiting to go straight or turn left. In an unsignalized intersection, the two-point turn generally takes longer than a vehicular left turn, because of the longer distance, because traffic is likely to be light if no signal is warranted, and because bicyclists must wait for a gap in more lanes before beginning the second leg of the two-point turn. In this case, the wait is shorter if there is a stop sign for the street from which the bicyclist initially approaches the intersection.

Inline bike box

An inline bike box can reduce delays for bicyclists only when motor traffic is congested and backs up at traffic signals, and when the bicyclists can overtake stopped motor traffic. The average delay for bicyclists who arrive on the red is 1/4 signal cycle in an intersection that gives equal time to the cross street, plus whatever time is required for left-turning bicyclists to yield to oncoming traffic, unless there is a special left-turn signal phase or advanced green.

When the light is green and motorists are passing through the bike box, bicyclists can not swerve left into the bike box to turn left. These bicyclists must wait on the green light and then proceed into the bike box on the red. Bicyclists who wait on the green light stand in the way of other bicyclists who could go straight through or turn right without waiting, and who otherwise would experience no delay. In jurisdictions with mandatory bike lane laws, bicyclists have no other lawful choice. The average delay for bicyclists who must wait on the green is 3/4 signal cycle, plus whatever time is needed to yield to oncoming traffic.

Sometimes a bike lane is provided between travel lanes rather than to their right, but no single bike lane can direct the bicyclist to the correct lane position for all destinations.

The average wait for left turns when swerving into the bike box is, then, 1/2 signal cycle waiting for the signal, plus the times waiting for traffic.

Another option for a left turn when arriving at the bike box on a green is to continue straight ahead and make a two-point turn as described at the start of this article, involving an average delay of 1/2 signal cycle. Other bicyclists waiting to enter the bike box may, as already described, block this maneuver.

Merging, and the vehicular left turn

Now, let's look at left turns in the absence of either type of bike box.

A bicyclist who signals and merges left before reaching the intersection, like other drivers, can almost always get the cooperation of an overtaking motorist. The bicyclist then can execute a vehicular left-turn. The vehicular left turn maneuver is explained on another page on this site.

Or the bicyclist may merge only far enough to deter a "right hook" (motor vehicle turning right from the bicyclist's left side), and then execute a two-point turn.

These maneuvers allow a bicyclist to approach the intersection at any time, as long as traffic is flowing freely. The delay for a two-point term is as with a cross-street bike box. The typical delay for a vehicular left turn is much shorter than for either type of bike box, except under congested traffic conditions. In an ordinary 4-leg signalized intersection without special left-turn signal phases, a vehicular left turn at a signalized intersection involves an average wait of 1/4 signal cycle when the bicyclist arrives on the red, or none when the bicyclist arrives on the green. Thus, the delay averages 1/8 signal cycle.

Motorists behind a left-turning bicyclist who want to go straight are less likely to have to wait than with the inline bike box, because they can often overtake the bicyclist on the right, and because the bicyclist may arrive at the intersection after the start of the green phase, rather than always starting just when the light turns green and opposite-direction traffic is heaviest. In a lane that carries both left-turning and through traffic, the bicyclist may, however, have to control the lane (wait in the center of the lane) to avoid motorists' overtaking on the right to turn left.

If traffic is queued up before the intersection, a bicyclist may move forward if there is an open lane to the right of a queue waiting to turn left. If all lanes are backed, up, filtering forward is more difficult, and is illegal in many jurisdictions. Even if there is a bike lane, the bicyclist must cut across through stopped traffic to reach the left-turn position. This requires caution that the next driver in each line of traffic has seen the bicyclist, before cutting across. In either case, the bicyclist is safest to wait behind the first stopped vehicle, which could start up without warning when the light changes.

Safety considerations

Cross-street bike box

Safety considerations with the cross-street bike box occur:

When the bicyclist is approaching the intersection. The bicyclist must, as mentioned already, negotiate with right-turning traffic, similarly to when traveling straight ahead. In congested or low-speed traffic, this negotiation is accomplished most efficiently and safely by merging into or to the left of the stream of right-turning traffic in order to avoid a "right hook" conflict, or by waiting in line before entering the intersection. The two-point turn facilitated by the cross-street bike box, however, avoids the need to merge farther to the left to a straight-through or vehicular left-turn position. In high-speed traffic, as on a rural highway, the bicyclist generally only checks for vehicles which are slowing and may turn right.

When the bicyclist is crossing the cross street and bearing right to enter the cross-street bike box. By bearing right, the bicyclist is taking a course that other road users may not expect. A driver in the street from which the bicyclist is coming may expect the bicyclist either to go straight or to make a right turn -- though this hazard is avoided by the lane positioning described above. A driver in the street into which the bicyclist is turning may expect the bicyclist to continue straight ahead. However, the bicyclist and other road users are generally in plain view of one another. Exception: in a multi-lane cross street, the sight line between the bicyclist and a vehicle in motion may be obstructed by waiting vehicles. This issue is most likely to arise where motorists can make a legal right turn on red, or at an unsignalized intersection. It can be avoided by placing the bike box out of the path of right-turning vehicles, or by prohibiting right turns on red at a signalized intersection.

When the bicyclist is completing the second leg of the two-point turn. The bicyclist crosses lanes of traffic, the same as when traveling straight in the cross street -- except for the avoidance of conflict with right-turning traffic as described in the previous bulleted point. The bicyclist must, however, cross all these lanes, and must scan for traffic from both directions rather than crossing only half the lanes with traffic from one direction, as in a vehicular left turn or a turn using an inline bike box.

With a cross-street bike box, there are safety issues for motorists in addition to those for conventional vehicular maneuvers. In particular, motorists in the cross street must wait farther back from the intersection, compromising their ability to scan for traffic before entering the intersection. Motorists may have to slow or stop again in the crosswalk or bike box to scan or yield right of way.

As the cross-street bike box is between the crosswalk and the intersection, it raises no issue of conflicts between bicyclists and pedestrians. Quite the contrary, bicyclists who might otherwise wait in the crosswalk to make a two-point turn now have their separate space.

All in all, the safety issues for a cross-street bike box are relatively minor, as long as it is placed out of conflict with right-turning traffic. The bicyclist follows a course that is mostly in plain view of other road users, and only moderately different from conventional and common bicycle and pedestrian movements.

Inline bike box

Safety issues with an inline bike box are more troublesome.

It is never safe for a bicyclist to swerve out in front of a motor vehicle that might start moving. For this reason, an inline box installation creates an inherent conflict in yielding rules under any of the following conditions.

if there is no traffic signal. Without a traffic signal, there is no predicting when motorists can start up. A stop sign is not an adequate substitute, for two reasons: it does not control the time when a motorist may restart, and also it does not control cross traffic. with a stop sign, a motorist would have to move forward through the bike box in order to look up and down the cross street for traffic.
if there is a traffic signal, but a right turn on red is permitted. In this case, a motorist also might enter the bike box at any time, and would also have to pull forward to scan for traffic in the cross street.
if there is not a special, active warning (signal) to indicate that the main traffic signal is about to turn green. This requirement is met in some installations in Europe with four-interval traffic signals, but is generally ignored in North America.

Lacking a special warning, the bicyclist might be able to use incidental information to figure out when the light is going to change to green. The bicyclist might, for example, notice that traffic in the cross street is coming to a stop -- however, there might be no traffic in the cross street.

If the pedestrian signal for a crosswalk on the near side of the cross street is in its walk phase, then the signal facing the bicyclist will not turn green soon, but on the other hand, the bicyclist might not be able to see that pedestrian signal early enough. A pedestrian signal for a concurrent walk phase for a crosswalk in the bicyclist's direction of travel usually changes at the same time as the green light comes on, or too shortly before to provide a useful warning. And with an exclusive walk phase, or a pushbutton-actuated signal, there is no reliable warning. A bicyclist in any case has no way to know how the pedestrian signal is actuated or timed.

All in all, lacking a special warning signal, the bicyclist then has no reliable way to know that it is safe to enter an inline bike box unless he or she has recently seen the light turn red.

A swerve into the bike box on a green light can not be made safely without yielding to overtaking traffic. But the look back at this point also is hazardous, because a bicyclist, like any driver about to enter the intersection, needs to be looking ahead for traffic in the intersection. It is preferable to merge into the flow of motor traffic well before the intersection and make a vehicular left turn or two-point turn.

An inline bike box becomes increasingly impractical on wider streets. That is because the bicyclist must cross more lanes of traffic to reach the left turn position, and the required warning time becomes longer. A British Web site suggests that application of a bike box is questionable when the bicyclist must cross into the second travel lane, and undesirable with more lanes. An inline bike box is therefore not practical at intersections where left turns are most difficult.

Legal considerations

Some jurisdictions have mandatory bike-lane laws, and depending on their wording, the bicyclist may not have the lawful option to make a vehicular left turn. The two-point turn, however, is legal almost everywhere if conducted with a stop and change of direction, and is a favored option for child and novice bicyclists. It delays the bicyclist no more than the left turn using the bike box, but much more than a vehicular left turn unless traffic is backed up heavily. Therefore, experienced bicyclists avoid the two-point turn except at the few locations where vehicular left turn is unlawful or impractical.

The traffic rules that follow are excerpted from the Uniform Vehicle Code, which is the basis for the traffic law of most US states.

Throughout the USA, a bicyclist is defined generally as having the rights and duties of a vehicle operator. Vehicle operators including bicyclists may overtake on the right under certain specified conditions.

11-304--When passing on the right is permitted

(a) The driver of a vehicle may overtake and pass upon the right of another vehicle only under the following conditions:

1. When the vehicle overtaken is making or about to make a left turn:

2. Upon a roadway with unobstructed pavement of sufficient width for two of more lines of vehicles moving lawfully in the direction being traveled by the overtaking vehicle.

(b) The driver of a vehicle may overtake and pass another vehicle upon the right only under conditions permitting such movement in safety. Such movement shall not be made by driving off the roadway.

This rule generally permits bicyclists to overtake cautiously on the right to approach a bike box.

Bicyclists generally may turn left either as vehicle operators, or with a two-point turn from the far right corner of the intersection, except if the following rule is applied :

11-1207--Left turns

(c) Notwithstanding the foregoing provisions, the state highway commission and local authorities in their respective jurisdictions may cause official traffic-control devices to be placed and thereby require and direct that specific course be traveled by turning bicycles or mopeds, and when such devices are so place, no person shall turn a bicycle or a moped other than as directed and required by such devices.

Under this rule, authorities may permit or require bicyclists to make left turns in special, nonstandard ways including use of the bike box. Many bicycling advocates dislike this rule, because it can be used to prohibit the generally faster vehicular left turn, and to make nonstandard and hazardous maneuvers mandatory at the whim of a jurisdiction with little understanding of bicycling. However, this rule applies only to left-turning bicyclists and not to bicyclists who are continuing straight through.

It is not illegal to merge out from the curb -- after all, this maneuver is necessary for any vehicle operator exiting a parking space. However, drivers must use caution:

11-604-- Turning movements and required signals

(a) No person shall turn a vehicle or move right or left upon a roadway unless and until such movement can be made with reasonable safety nor without giving an appropriate signal in the manner hereinafter provided.

A motorist preparing to enter traffic from a parking space can wait until there is no conflicting traffic. A bicyclist in the bike box must swerve directly in front of vehicles which could start up when the light changes --and so the requirement that a turning movement be made only in reasonable safety can not be met without an active warning signal. Consider: who is to be held at fault for a collision resulting from the lack of a warning: the motorist, the bicyclist or the jurisdiction?

Recommendations

The cross-street bike box may be a valid option when it avoids the need to merge across multiple lanes of traffic and wait in a long queue. A cross-street bike box is relatively free of problems and conflicts, and does not require signalization, though there is rarely justification for a cross-street bike box in an intersection which does not warrant signalization.

Where there is very heavy traffic bicycle and motor traffic going straight through, an inline bike box may sometimes decrease delays for bicyclists, at the expense of increased delays for motorists. An inline bike box is much more problematic when it is used for left turns or to cross to the far side of a one-way street, because in these cases, the bicyclist must wait on the green light to enter the bike box and then must wait on the red. The problems of a bike box increase with its width, and so a bike box is not useful for left turns on the multi-lane arterials where left turns are most challenging.

The inline bike box is acceptable only at an intersection with traffic signals, and only ever decreases bicyclists' travel time if they can overtake queued traffic. Overtaking is generally facilitated by a bike lane to the right of the other lanes. Overtaking on the right, however, poses risks of collisions where vehicles can cross or turn to enter or exit streets or driveways, or if pedestrians jaywalk through the stopped traffic, or if the bicyclist is within range of opening car doors on either the right or the left...the list goes on. Generally, it is only safe to overtake slowly on the right, and often it is not safe at all.

Either type of bike box can make a left turn easier and faster only when traffic is heavy, and even then, the bike box often involves more delay than a vehicular left turn. Use of a bike box should therefore never be mandatory. Bicyclists should be permitted to cross intersections according to normal vehicular or pedestrian rules.

A "right hook" collision can occur between a bicyclist and a right-turning vehicle with either type of bike box. But with the inline bike box, there is an additional risk if a bicyclist turns left in front of a motor vehicle just as the traffic light turns green. This risk is very serious with a large vehicle whose driver can not see a bicyclist next to the vehicle's right front corner. Though a bicyclist might be held at fault for turning out across the street when it is not safe, the jurisdiction also might be held at fault for encouraging this action, particularly if the bicyclist is a child and a higher standard of care applies. The hazard can only be properly addressed by providing an active warning signal.

References:

A critique of an installation may be found at: "Bike box" at Garden Street and Concord Avenue, Cambridge, Massachusetts.

An illustration of a four-interval traffic signal and a list of countries in which it is used may be found at http://en.wikipedia.org/wiki/Traffic_light

http://www.dft.gov.uk/pgr/roads/tpm/tal/cyclefacilities/advancedstoplines shows bike box installations with approach bike lanes and lists locations in the UK where bike boxes have been tried.

www.camcycle.org.uk/campaigning/papers/AdvancedStopLines.pdf -- page 4 of the PDF shows a dual-signal installation. However, cyclists are passing the first signal on the red. It is unclear whether the timing of the two signals is different so as to give bicyclists a warning, or whether the cyclists are proceeding lawfully. Page 7 shows a separate bicycle signal, but used to give bicyclists a head start. This document gives a survey of bike box installations in Cambridge, England, and favors them, though it advocates a large enough number of improvements to cast doubt on its positive evaluation.

http://www.westminstercyclists.org.uk/ (click on link "do advanced stop lines work") The data reviewed here indicate that motorist encroachment into the bike box is a major concern.

British research on feeder lanes for bike boxes

A description of a bike box in Vancouver, BC

A LOOK INTO THE "BIKE BOX"

What is a "bike box"

The cross-street bike box

The inline bike box

Operational characteristics

Cross-street bike box

Inline bike box

Merging, and the vehicular left turn

Safety considerations

Cross-street bike box

Inline bike box

Legal considerations

Recommendations

References: