Advocates for bike lanes tend to fall on the city planning and urban design side of things (in general, but there are some noted exceptions). They argue, correctly I think, that the lanes tend to have a traffic calming effect and that they have the potential to complete the streets and make them more pedestrian friendly. Slower traffic and quiet vehicles like bicycles do make for a more pleasing atmosphere in a street scape. It comes as no surprise to me that people who advocate the construction of these lanes point to notable examples like Copenhagen and Portland, which feature some very lovely urban environments.
As a rebuttal to the more engineering-minded opponents of cycling lanes, they suggest that safety comes in greater numbers, and that the increase in mode-share is more important than some perfectly designed road solution (as noted by opponents, there are some potentially major flaws in several bike lane designs). There appears to be some truth to this suggestion, and according to several sources, injuries in some cities adopting lanes have remained relatively flat while ridership has gradually increased.
Opponents of bike lanes are practically minded individuals who recognize shortcomings of bike lanes that have yet to be overcome. Most notably amongst them is that paint on pavement doesn't stop motorists from treating cyclists as a different class of vehicle. For example, cars will cross over a lane of travel to make turns and thus block the bike lane (which is typically located on the outside edge of the road). Other concerns worthy of consideration are the loss of available lanes or on street parking for vehicles, or safety hazards presented by placing bike lanes in the 'door zone' of parked vehicles, as is done in Chicago, and a major one for Dallas to consider is the added expense of upkeep for the bike lanes, but we will come back to this in a moment.
Major opponents of bike lanes largely fall into the vehicular cyclist category and believe that bicycles should be treated as vehicles just like cars or trucks, and should enjoy the same rights, previlges and responsibilities. They note that even in the most developed city, bike lanes can't be everywhere, and eventually riders will need to ride in the street. The solution to the problem, in their minds, is proper education to overcome fear and to ride confidently and safely. While education is probably the only way to fight ignorance, the fear of riding alongside monster trucks and SUV's going over 40 miles per hour is quite a lot to overcome, and like it or not, people do feel safer behind a stripe.
Now, having said all of this, the truth is that both sides of the debate want the same thing: Increased, safer ridership and a decreased dependency on automobiles. I would bet dollars to donuts that everyone in this debate probably voted for the same presidential candidate. What Dallas needs is both education and facilities, with a focus and purpose. There are certain roads where the disparity between bicycles and vehicle speeds are simply too great. Just because we have a legal right to be there doesn't necessarily mean that we belong there.
What is surprising about the Dallas bike plan is that it suggests putting facilities where they are needed the least: Downtown Dallas. It is rare when a vehicle can achieve speeds near 30 miles per hour, and there are several alternative routes with varying degrees of traffic. Think of these like ski slopes. There are 'Green' trails that are easy for everybody, like Jackson Street, and then there are 'Black Diamonds' which demand a little more confidence and focus, like Ross or Commerce. None are so challenging that someone with the right information and a little confidence couldn't ride, even in rush hour.
What is a challenge though is riding a major arterial in the surrounding suburbs, where there is little to reduce the speed of motor vehicles or to amend their driving habits to be safer. Even when I take the lane on Live Oak (arguable one of the more quiet arterials of East Dallas) cars pass too closely, mostly because there is speed and room to straddle the lanes (which is illegal, but since when have laws prevented people from driving like jackasses?)
As a practical matter, the streets in the northern areas of Dallas tend to be in much better shape than the streets near downtown. I suspect that this has something to do with tax revenue in these areas, but I'm not entirely sure. Knowing that more resources are dedicated there rather than Downtown, it should be obvious that bike lanes there are likely to be maintained better than in the heart of Dallas. Streets in Downtown are constantly patched with steel plates or piss poor asphalt fills that can be hazardous to cyclists. There is debris in the street, not just the gutters, because the budgets have been cut for street maintenance.
So to me, a bike lane or cycle track down the Northwest Highway makes far more sense, even though ridership probably won't be that high. Putting one down Elm or Commerce really doesn't make a lot of sense, especially if it is shared with city buses (constant stops, erratic and illegal driving, large and intimidating vehicles, hot and smelly exhaust, even with the natural gas. Does this sound inviting to new riders?).
What is the solution? I don't think there is one in the short term, but both parties are right. There should be a serious education effort made now with school age children to encourage the use of bicycles for transportation, and they should learn how to ride properly, both in bike lanes where provided, and in the street where they are not. Vehicular cyclists are right on this point because there will be many occasions where bike lanes are not provided and they should ride as safely and knowledgeably as possible. Bike lanes will NEVER be a replacement for knowledge and education.
Safety DOES come in greater numbers, and if it takes a bike lane to get a greater number of riders from a high speed area to somewhere that is more manageable for vehicular cycling, so be it. But even with these lanes, it does not totally erase the safety issues that the interaction of motor vehicles and bicycles brings. Knowledge is still a must for safely navigating the streets. But as the number of cyclists increases, the awareness on behalf of operators of motor vehicles will increase as well.
To sum it all up, nothing productive will happen unless both sides of the debate embrace each other, and present a unified front to get more people out on the street cycling for practical purposes. Advocates should understand that bike lanes aren't the cure-all to urban woes that they think they are, and opponents should agree that, provided they are not made mandatory, and are only provided in areas where they are likely to increase ridership, there is no problem with bike lanes as long as education of cyclists is still a must.