Clogged downtown intersections haven't led to citations, yet, as Houston officials redouble efforts to keep cars and trucks - and yes, buses - from blocking lanes and keeping peak traffic trapped in the business district.

Considered by many one of the most frustrating features of downtown driving, multiple blocks of the central business district can grind to a halt when vehicles block intersections and traffic lights change the flow of traffic. When it occurs, drivers who get a green light find themselves stuck to the side of automobiles - and yes, buses - unable to clear the crossing.

Asked about the phenomenon, Robert Walfort, 41, cursed, noting he sees intersections blocked frequently on his way to and from work along Dallas and Lamar.

"Every d--- day," Walfort said, adding later, "how some of these people have (driver's) licenses is beyond me."

Equally frustrated by a street grid locked by drivers dashing into the intersection - which also makes for tough walking for pedestrians - city officials are working on a host of remedies, or at least attempts at remedies. Houston Public Works has painted crisscross patterns in some downtown intersections and erected signs telling people "don't block the box," a reference to keeping lanes and pedestrian crossings clear. Signs started going in about a year ago, with more added in recent months.

Austin has had similar success with a campaign aimed at clearing intersections, which included additional enforcement of the law after the intersections were signed. Pearland also adopted a "don't block the box" campaign, notably along key intersections of FM 518.

In Houston, police spokesman Victor Senties said officers "are focusing attention on improving mobility downtown," but stopped short of discussing enforcement efforts.

"Don't take it as anybody being targeted," Senties said.

Local public transit agencies said police have called them to discuss intersection clearance.

"They were real friendly about it," said Chris LaRue, transit program manager for The Woodlands Township. "They were telling us to make sure and not block the lanes, which I understand."

Buses that get stuck can easily block two and sometimes three lanes of opposing traffic. Extremely large buses, such as the 60-foot articulated buses Metropolitan Transit Authority uses on some high-frequency routes, can block an entire five-lane road.

"It is a little easier for a passenger car or small truck to whip into the other lane," LaRue said. "We can't really do that."

Outside of the peak commuting times, problems are minimal. During high-volume times, however, the flow can overwhelm the capacity, some blocked lanes only compound. Streets in the central business district that are common entrance and exit routes to the freeways can average 10,000 to 17,000 vehicles on a typical work day, based on Houston's 2014 traffic counts. Park and rides buses increase in frequency during peak commuting times, with some lanes of major streets restricted to buses and turning vehicles to accommodate the increased transit use.

Public works also updates traffic signal timing on a rotating basis around Houston, including the central business district, last updated in late 2015 and early 2016. Each of the roughly 2,450 signalized intersections in the city are updated every three years, with adjustments periodically.

In the past 18 months, officials also have grappled with re-timing lights related to the opening of Metro's east-west train lines, which flow in lanes with passenger vehicles along Capitol and Rusk. The trains, which pose the same problems of blocking intersections as large trucks and buses, halt traffic in lanes at rail stations, and limit right turns from Rusk.