WASHINGTON — A driver jumped a curb and plowed into an informational sign near the White House Monday morning — prompting police to make a dramatic arrest while the Secret Service imposed a brief lockdown around the executive mansion. The sedan drove onto the sidewalk just north of Lafayette Park around 10 a.m., but did not get anywhere near the executive mansion’s gates more than a block away. At almost the same time, a different man jumped over a security barrier about two blocks away and was arrested by the Secret Service. Uniformed protective agents led the driver away in handcuffs. The motorist could be heard shouting “oh my God!” as he was marched down Pennsylvania Avenue. The intersection’s layout — which forces oncoming traffic to traverse a single cobblestone lane on 16th Street NW before making a left turn at a traffic light onto H Street — makes it difficult to accelerate quickly. The area of the crash is commonly frequented by pedestrians and tourists looking for selfies with the White House in the background, but there were no immediate reports of injuries.